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SYNOPSIS
Tests if all elements of an array are non-zero
USAGE
Char_Type all (Array_Type a [,Int_Type dim])
DESCRIPTION
The `all' function examines the elements of a numeric array and
returns 1 if all elements are non-zero, otherwise it returns 0. If a
second argument is given, then it specifies the dimension of the
array over which the function is to be applied. In this case, the
result will be an array with the same shape as the input array minus
the specified dimension.
EXAMPLE
Consider the 2-d array
1 2 3 4 5
6 7 8 9 10
generated by
a = _reshape ([1:10], [2, 5]);
Then `all(a)' will return 1, and `all(a>3, 0)' will return
a 1-d array
[0, 0, 0, 1, 1]
Similarly, `all(a>3, 1)' will return the 1-d array
[0,1]
SEE ALSO
where, any
--------------------------------------------------------------
any
SYNOPSIS
Test if any element of an array is non-zero
USAGE
Char_Type any (Array_Type a [,Int_Type dim])
DESCRIPTION
The `any' function examines the elements of a numeric array and
returns 1 if any element is both non-zero and not a NaN, otherwise
it returns 0. If a second argument is given, then it specifies
the dimension of the array to be tested.
EXAMPLE
Consider the 2-d array
1 2 3 4 5
6 7 8 9 10
generated by
a = _reshape ([1:10], [2, 5]);
Then `any(a==3)' will return 1, and `any(a==3, 0)'
will return a 1-d array with elements:
0 0 1 0 0
SEE ALSO
where, all
--------------------------------------------------------------
array_info
SYNOPSIS
Returns information about an array
USAGE
(Array_Type, Integer_Type, DataType_Type) array_info (Array_Type a)
DESCRIPTION
The `array_info' function returns information about the array `a'.
It returns three values: an 1-d integer array specifying the
size of each dimension of `a', the number of dimensions of
`a', and the data type of `a'.
EXAMPLE
The `array_info' function may be used to find the number of rows
of an array:
define num_rows (a)
{
variable dims, num_dims, data_type;
(dims, num_dims, data_type) = array_info (a);
return dims [0];
}
SEE ALSO
typeof, array_info, array_shape, length, reshape, _reshape
--------------------------------------------------------------
array_map
SYNOPSIS
Apply a function to each element of an array
USAGE
Array_Type array_map (type, func, arg0, ...)
DataType_Type type;
Ref_Type func;
DESCRIPTION
The `array_map' function may be used to apply a function to each
element of an array and returns the resulting values as an array of
the specified type. The `type' parameter indicates what kind of
array should be returned and generally corresponds to the return
type of the function. The `arg0' parameter should be an array
and is used to determine the dimensions of the resulting array. If
any subsequent arguments correspond to an array of the same size,
then those array elements will be passed in parallel with the first
arrays arguments.
EXAMPLE
The first example illustrates how to apply the `strlen' function
to an array of strings:
S = ["", "Train", "Subway", "Car"];
L = array_map (Integer_Type, &strlen, S);
This is equivalent to:
S = ["", "Train", "Subway", "Car"];
L = Integer_Type [length (S)];
for (i = 0; i < length (S); i++) L[i] = strlen (S[i]);
Now consider an example involving the `strcat' function:
files = ["slang", "slstring", "slarray"];
exts = ".c";
cfiles = array_map (String_Type, &strcat, files, exts);
% ==> cfiles = ["slang.c", "slstring.c", "slarray.c"];
exts = [".a",".b",".c"];
xfiles = array_map (String_Type, &strcat, files, exts);
% ==> xfiles = ["slang.a", "slstring.b", "slarray.c"];
NOTES
Many mathematical functions already work transparantly on arrays.
For example, the following two statements produce identical results:
B = sin (A);
B = array_map (Double_Type, &sin, A);
SEE ALSO
array_info, strlen, strcat, sin
--------------------------------------------------------------
array_reverse
SYNOPSIS
Reverse the elements of an array
USAGE
array_reverse (Array_Type a [,Int_Type i0, Int_Type i1] [,Int_Type dim])
DESCRIPTION
In its simplest form, the `array_reverse' function reverses the
elements of an array. If passed 2 or 4 arguments,
`array_reverse' reverses the elements of the specified
dimension of a multi-dimensional array. If passed 3 or 4 arguments,
the parameters `i0' and `i1' specify a range of elements
to reverse.
EXAMPLE
If `a' is a one dimensional array, then
array_reverse (a, i, j);
a[[i:j]] = a[[j:i:-1]];
are equivalent to one another. However, the form using
`array_reverse' is about 10 times faster than the version that
uses explicit array indexing.
SEE ALSO
array_swap, transpose
--------------------------------------------------------------
array_shape
SYNOPSIS
Get the shape or dimensions of an array
USAGE
dims = array_shape (Array_Type a)
DESCRIPTION
This function returns an array representing the dimensionality or
shape of a specified array. The `array_info' function also
returns this information but for many purposes the
`array_shape' function is more convenient.
SEE ALSO
array_info, reshape
--------------------------------------------------------------
array_sort
SYNOPSIS
Sort an array
USAGE
Array_Type array_sort (Array_Type a [, String_Type or Ref_Type f])
DESCRIPTION
`array_sort' sorts the array `a' into ascending order and
returns an integer array that represents the result of the sort. If
the optional second parameter `f' is present, the function
specified by `f' will be used to compare elements of `a';
otherwise, a built-in sorting function will be used.
If `f' is present, then it must be either a string representing
the name of the comparison function, or a reference to the function.
The sort function represented by `f' must be a S-Lang function
that takes two arguments. The function must return an integer that
is less than zero if the first parameter is considered to be less
than the second, zero if they are equal, and a value greater than
zero if the first is greater than the second.
If the comparison function is not specified, then a built-in comparison
function appropriate for the data type will be used. For example,
if `a' is an array of character strings, then the sort will be
performed using the `strcmp' function.
The integer array returned by this function is simply an index array
that indicates the order of the sorted array. The input array
`a' is not changed.
EXAMPLE
An array of strings may be sorted using the `strcmp' function
since it fits the specification for the sorting function described
above:
A = ["gamma", "alpha", "beta"];
I = array_sort (A, &strcmp);
Alternatively, one may use
variable I = array_sort (A);
to use the built-in comparison function.
After the `array_sort' has executed, the variable `I' will
have the values `[2, 0, 1]'. This array can be used to
re-shuffle the elements of `A' into the sorted order via the
array index expression `A = A[I]'. This operation may also be
written:
A = A[array_sort(A)];
SEE ALSO
strcmp
--------------------------------------------------------------
array_swap
SYNOPSIS
Swap elements of an array
USAGE
array_swap (Array_Type a, Int_Type i, Int_Type j)
DESCRIPTION
The `array_swap' function swaps the specified elements of an
array. It is equivalent to
(a[i], a[j]) = (a[j], a[i]);
except that it executes several times faster than the above construct.
SEE ALSO
array_reverse, transpose
--------------------------------------------------------------
cumsum
SYNOPSIS
Compute the cumulative sum of an array
USAGE
result = cumsum (Array_Type a [, Int_Type dim])
DESCRIPTION
The `cumsum' function performs a cumulative sum over the
elements of a numeric array and returns the result. If a second
argument is given, then it specifies the dimension of the array to
be summed over. For example, the cumulative sum of
`[1,2,3,4]', is the array `[1,1+2,1+2+3,1+2+3+4]', i.e.,
`[1,3,6,10]'.
SEE ALSO
sum
--------------------------------------------------------------
init_char_array
SYNOPSIS
Initialize an array of characters
USAGE
init_char_array (Array_Type a, String_Type s)
DESCRIPTION
The `init_char_array' function may be used to initialize a
character array `a' by setting the elements of the array
`a' to the corresponding characters of the string `s'.
EXAMPLE
The statements
variable a = Char_Type [10];
init_char_array (a, "HelloWorld");
creates an character array and initializes its elements to the
characters in the string `"HelloWorld"'.
NOTES
The character array must be large enough to hold all the characters
of the initialization string.
SEE ALSO
bstring_to_array, strlen, strcat
--------------------------------------------------------------
_isnull
SYNOPSIS
Check an array for NULL elements
USAGE
Char_Type[] = _isnull (a[])
DESCRIPTION
This function may be used to test for the presence of NULL elements
of an array. Specifically, it returns a Char_Type array of
with the same number of elements and dimensionality of the input
array. If an element of the input array is NULL, then the
corresponding element of the output array will be set to 1,
otherwise it will be set to 0.
EXAMPLE
Set all NULL elements of a string array `A' to the empty
string `""':
A[where(_isnull(A))] = "";
NOTES
It is important to understand the difference between `A==NULL'
and `_isnull(A)'. The latter tests all elements of `A'
against NULL, whereas the former only tests `A' itself.
SEE ALSO
where, array_map
--------------------------------------------------------------
length
SYNOPSIS
Get the length of an object
USAGE
Integer_Type length (obj)
DESCRIPTION
The `length' function may be used to get information about the
length of an object. For simple scalar data-types, it returns 1.
For arrays, it returns the total number of elements of the array.
NOTES
If `obj' is a string, `length' returns 1 because a
String_Type object is considered to be a scalar. To get the
number of characters in a string, use the `strlen' function.
SEE ALSO
array_info, array_shape, typeof, strlen
--------------------------------------------------------------
max
SYNOPSIS
Get the maximum value of an array
USAGE
result = max (Array_Type a [,Int_Type dim])
DESCRIPTION
The `max' function examines the elements of a numeric array and
returns the value of the largest element. If a second argument is
given, then it specifies the dimension of the array to be searched.
In this case, an array of dimension one less than that of the input array
will be returned with the corresponding elements in the specified
dimension replaced by the maximum value in that dimension.
EXAMPLE
Consider the 2-d array
1 2 3 4 5
6 7 8 9 10
generated by
a = _reshape ([1:10], [2, 5]);
Then `max(a)' will return `10', and `max(a,0)' will return
a 1-d array with elements
6 7 8 9 10
NOTES
This function ignores NaNs in the input array.
SEE ALSO
min, sum, reshape
--------------------------------------------------------------
min
SYNOPSIS
Get the minimum value of an array
USAGE
result = min (Array_Type a [,Int_Type dim])
DESCRIPTION
The `min' function examines the elements of a numeric array and
returns the value of the smallest element. If a second argument is
given, then it specifies the dimension of the array to be searched.
In this case, an array of dimension one less than that of the input array
will be returned with the corresponding elements in the specified
dimension replaced by the minimum value in that dimension.
EXAMPLE
Consider the 2-d array
1 2 3 4 5
6 7 8 9 10
generated by
a = _reshape ([1:10], [2, 5]);
Then `min(a)' will return `1', and `min(a,0)' will return
a 1-d array with elements
1 2 3 4 5
NOTES
This function ignores NaNs in the input array.
SEE ALSO
max, sum, reshape
--------------------------------------------------------------
_reshape
SYNOPSIS
Copy an array to a new shape
USAGE
Array_Type _reshape (Array_Type A, Array_Type I)
DESCRIPTION
The `_reshape' function creates a copy of an array `A',
reshapes it to the form specified by `I' and returns the result.
The elements of `I' specify the new dimensions of the copy of
`A' and must be consistent with the number of elements `A'.
EXAMPLE
If `A' is a `100' element 1-d array, a new 2-d array of
size `20' by `5' may be created from the elements of `A'
by
B = _reshape (A, [20, 5]);
NOTES
The `reshape' function performs a similar function to
`_reshape'. In fact, the `_reshape' function could have been
implemented via:
define _reshape (a, i)
{
a = @a; % Make a new copy
reshape (a, i);
return a;
}
SEE ALSO
reshape, array_shape, array_info
--------------------------------------------------------------
reshape
SYNOPSIS
Reshape an array
USAGE
reshape (Array_Type A, Array_Type I)
DESCRIPTION
The `reshape' function changes the shape of `A' to have the
shape specified by the 1-d integer array `I'. The elements of `I'
specify the new dimensions of `A' and must be consistent with
the number of elements `A'.
EXAMPLE
If `A' is a `100' element 1-d array, it can be changed to a
2-d `20' by `5' array via
reshape (A, [20, 5]);
However, `reshape(A, [11,5])' will result in an error because
the `[11,5]' array specifies `55' elements.
NOTES
Since `reshape' modifies the shape of an array, and arrays are
treated as references, then all references to the array will
reference the new shape. If this effect is unwanted, then use the
`_reshape' function instead.
SEE ALSO
_reshape, array_info, array_shape
--------------------------------------------------------------
sum
SYNOPSIS
Sum over the elements of an array
USAGE
result = sum (Array_Type a [, Int_Type dim])
DESCRIPTION
The `sum' function sums over the elements of a numeric array and
returns its result. If a second argument is given, then it
specifies the dimension of the array to be summed over. In this
case, an array of dimension one less than that of the input array
will be returned.
If the input array is an integer type, then the resulting value will
be a Double_Type. If the input array is a Float_Type,
then the result will be a Float_Type.
EXAMPLE
The mean of an array `a' of numbers is
sum(a)/length(a)
SEE ALSO
cumsum, transpose, reshape
--------------------------------------------------------------
transpose
SYNOPSIS
Transpose an array
USAGE
Array_Type transpose (Array_Type a)
DESCRIPTION
The `transpose' function returns the transpose of a specified
array. By definition, the transpose of an array, say one with
elements `a[i,j,...k]' is an array whose elements are
`a[k,...,j,i]'.
SEE ALSO
_reshape, reshape, sum, array_info, array_shape
--------------------------------------------------------------
where
USAGE
Array_Type where (Array_Type a [, Ref_Type jp])
DESCRIPTION
The `where' function examines a numeric array `a' and
returns an integer array giving the indices of `a'
where the corresponding element of `a' is non-zero. The
function accepts an optional Ref_Type argument that will be
set to complement set of indices, that is, the indices where
`a' is zero. In fact
i = where (a);
j = where (not a);
and
i = where (a, &j);
are equivalent, but the latter form is prefered since it executes
about twice as fast as the former.
Although this function may appear to be simple or even trivial, it
is arguably one of the most important and powerful functions for
manipulating arrays.
EXAMPLE
Consider the following:
variable X = [0.0:10.0:0.01];
variable A = sin (X);
variable I = where (A < 0.0);
A[I] = cos (X) [I];
Here the variable `X' has been assigned an array of doubles
whose elements range from `0.0' through `10.0' in
increments of `0.01'. The second statement assigns `A' to
an array whose elements are the `sin' of the elements of `X'.
The third statement uses the `where' function to get the indices of
the elements of `A' that are less than 0. Finally, the
last statement replaces those elements of `A' by the cosine of the
corresponding elements of `X'.
NOTES
Support for the optional argument was added to version 2.1.0.
SEE ALSO
wherefirst, wherelast, wherenot, array_info, array_shape, _isnull
--------------------------------------------------------------
wherenot
SYNOPSIS
Get indices where a numeric array is 0
USAGE
Array_Type wherenot (Array_Type)
DESCRIPTION
This function is equivalent to `where(not a)'. See the
documentation for `where' for more information.
SEE ALSO
where, wherefirst, wherelast
--------------------------------------------------------------
wherefirst
SYNOPSIS
Get the index of the first non-zero array element
USAGE
Int_Type wherefirst (Array_Type a [,start_index])
DESCRIPTION
The `wherefirst' function returns the index of the first
non-zero element of a specified array. If the optional parameter
`start_index' is given, the search will take place starting
from that index. If a non-zero element is not found, the function
will return NULL.
NOTES
The single parameter version of this function is equivalent to
define wherefirst (a)
{
variable i = where (a);
if (length(i))
return i[0];
else
return NULL;
}
SEE ALSO
where, wherelast
--------------------------------------------------------------
wherelast
SYNOPSIS
Get the index of the last non-zero array element
USAGE
Int_Type wherelast (Array_Type a [,start_index])
DESCRIPTION
The `wherelast' function returns the index of the last
non-zero element of a specified array. If the optional parameter
`start_index' is given, the backward search will take place starting
from that index. If a non-zero element is not found, the function
will return NULL.
NOTES
The single parameter version of this function is equivalent to
define wherefirst (a)
{
variable i = where (a);
if (length(i))
return i[-1];
else
return NULL;
}
SEE ALSO
where, wherefirst
--------------------------------------------------------------
assoc_delete_key
SYNOPSIS
Delete a key from an Associative Array
USAGE
assoc_delete_key (Assoc_Type a, String_Type k)
DESCRIPTION
The `assoc_delete_key' function deletes a key given by `k'
from the associative array `a'. If the specified key does not
exist in `a', then this function has no effect.
SEE ALSO
assoc_key_exists, assoc_get_keys
--------------------------------------------------------------
assoc_get_keys
SYNOPSIS
Return all the key names of an Associative Array
USAGE
String_Type[] assoc_get_keys (Assoc_Type a)
DESCRIPTION
This function returns all the key names of an associative array
`a' as an ordinary one dimensional array of strings. If the
associative array contains no keys, an empty array will be returned.
SEE ALSO
assoc_get_values, assoc_key_exists, assoc_delete_key, length
--------------------------------------------------------------
assoc_get_values
SYNOPSIS
Return all the values of an Associative Array
USAGE
Array_Type assoc_get_keys (Assoc_Type a)
DESCRIPTION
This function returns all the values in the associative array
`a' as an array of proper type. If the associative array
contains no keys, an empty array will be returned.
EXAMPLE
Suppose that `a' is an associative array of type
Integer_Type, i.e., it was created via
variable a = Assoc_Type[Integer_Type];
The the following may be used to print the values of the array in
ascending order:
static define int_sort_fun (x, y)
{
return sign (x - y);
}
define sort_and_print_values (a)
{
variable v = assoc_get_values (a);
variable i = array_sort (v, &int_sort_fun);
v = v[i];
foreach (v)
{
variable vi = ();
() = fprintf (stdout, "%d\n", vi);
}
}
SEE ALSO
assoc_get_values, assoc_key_exists, assoc_delete_key, array_sort
--------------------------------------------------------------
assoc_key_exists
SYNOPSIS
Check to see whether a key exists in an Associative Array
USAGE
Integer_Type assoc_key_exists (Assoc_Type a, String_Type k)
DESCRIPTION
The `assoc_key_exists' function may be used to determine whether
or not a specified key `k' exists in an associative array `a'.
It returns 1 if the key exists, or 0 if it does not.
SEE ALSO
assoc_get_keys, assoc_get_values, assoc_delete_key
--------------------------------------------------------------
array_to_bstring
SYNOPSIS
Convert an array to a binary string
USAGE
BString_Type array_to_bstring (Array_Type a)
DESCRIPTION
The `array_to_bstring' function returns the elements of an
array `a' as a binary string.
SEE ALSO
bstring_to_array, init_char_array
--------------------------------------------------------------
bstring_to_array
SYNOPSIS
Convert a binary string to an array of characters
USAGE
UChar_Type[] bstring_to_array (BString_Type b)
DESCRIPTION
The `bstring_to_array' function returns an array of unsigned
characters whose elements correspond to the characters in the
binary string.
SEE ALSO
array_to_bstring, init_char_array
--------------------------------------------------------------
bstrlen
SYNOPSIS
Get the length of a binary string
USAGE
UInt_Type bstrlen (BString_Type s)
DESCRIPTION
The `bstrlen' function may be used to obtain the length of a
binary string. A binary string differs from an ordinary string (a C
string) in that a binary string may include null chracters.
EXAMPLE
s = "hello\0";
len = bstrlen (s); % ==> len = 6
len = strlen (s); % ==> len = 5
SEE ALSO
strlen, length
--------------------------------------------------------------
pack
SYNOPSIS
Pack objects into a binary string
USAGE
BString_Type pack (String_Type fmt, ...)
DESCRIPTION
The `pack' function combines zero or more objects (represented
by the ellipses above) into a binary string according to the format
string `fmt'.
The format string consists of one or more data-type specification
characters defined by the following table:
c char
C unsigned char
h short
H unsigned short
i int
I unsigned int
l long
L unsigned long
m long long
M unsigned long long
j 16 bit int
J 16 bit unsigned int
k 32 bit int
K 32 bit unsigned int
q 64 bit int
Q 64 bit unsigned int
f float
d double
F 32 bit float
D 64 bit float
s character string, null padded
S character string, space padded
z character string, null padded
x a null pad character
A decimal length specifier may follow the data-type specifier. With
the exception of the `s' and `S' specifiers, the length
specifier indicates how many objects of that data type are to be
packed or unpacked from the string. When used with the `s',
`S', or `z' specifiers, it indicates the field width to be
used. If the length specifier is not present, the length defaults
to one.
When packing, unlike the `s' specifier, the `z' specifier
guarantees that at least one null byte will be written even if the
field has to be truncated to do so.
With the exception of `c', `C', `s', `S', and
`x', each of these may be prefixed by a character that indicates
the byte-order of the object:
> big-endian order (network order)
< little-endian order
= native byte-order
The default is to use native byte order.
When unpacking via the `unpack' function, if the length
specifier is greater than one, then an array of that length will be
returned. In addition, trailing whitespace and null characters are
stripped when unpacking an object given by the `S' specifier.
Trailing null characters will be stripped from an object represented
by the `z' specifier. No such stripping is performed by the `s'
specifier.
EXAMPLE
a = pack ("cc", 'A', 'B'); % ==> a = "AB";
a = pack ("c2", 'A', 'B'); % ==> a = "AB";
a = pack ("xxcxxc", 'A', 'B'); % ==> a = "\0\0A\0\0B";
a = pack ("h2", 'A', 'B'); % ==> a = "\0A\0B" or "\0B\0A"
a = pack (">h2", 'A', 'B'); % ==> a = "\0\xA\0\xB"
a = pack ("<h2", 'A', 'B'); % ==> a = "\0B\0A"
a = pack ("s4", "AB", "CD"); % ==> a = "AB\0\0"
a = pack ("s4s2", "AB", "CD"); % ==> a = "AB\0\0CD"
a = pack ("S4", "AB", "CD"); % ==> a = "AB "
a = pack ("S4S2", "AB", "CD"); % ==> a = "AB CD"
a = pack ("z4", "AB"); % ==> a = "AB\0\0"
a = pack ("s4", "ABCDEFG"); % ==> a = "ABCD"
a = pack ("z4", "ABCDEFG"); % ==> a = "ABC\0"
SEE ALSO
unpack, sizeof_pack, pad_pack_format, sprintf
--------------------------------------------------------------
pad_pack_format
SYNOPSIS
Add padding to a pack format
USAGE
BString_Type pad_pack_format (String_Type fmt)
DESCRIPTION
The `pad_pack_format' function may be used to add the
appropriate padding characters to the format `fmt' such that the
data types specified by the format will be properly aligned on word
boundaries. This is especially important when reading or writing files
that assume the native alignment.
SEE ALSO
pack, unpack, sizeof_pack
--------------------------------------------------------------
sizeof_pack
SYNOPSIS
Compute the size implied by a pack format string
USAGE
UInt_Type sizeof_pack (String_Type fmt)
DESCRIPTION
The `sizeof_pack' function returns the size of the binary string
represented by the format string `fmt'. This information may be
needed when reading a structure from a file.
SEE ALSO
pack, unpack, pad_pack_format
--------------------------------------------------------------
unpack
SYNOPSIS
Unpack Objects from a Binary String
USAGE
(...) = unpack (String_Type fmt, BString_Type s)
DESCRIPTION
The `unpack' function unpacks objects from a binary string
`s' according to the format `fmt' and returns the objects to
the stack in the order in which they were unpacked. See the
documentation of the `pack' function for details about the
format string.
EXAMPLE
(x,y) = unpack ("cc", "AB"); % ==> x = 'A', y = 'B'
x = unpack ("c2", "AB"); % ==> x = ['A', 'B']
x = unpack ("x<H", "\0\xAB\xCD"); % ==> x = 0xCDABuh
x = unpack ("xxs4", "a b c\0d e f"); % ==> x = "b c\0"
x = unpack ("xxS4", "a b c\0d e f"); % ==> x = "b c"
SEE ALSO
pack, sizeof_pack, pad_pack_format
--------------------------------------------------------------
Assoc_Type
SYNOPSIS
An associative array or hash type
DESCRIPTION
An Assoc_Type object is like an array except that it is
indexed using strings and not integers. Unlike an Array_Type
object, the size of an associative array is not fixed, but grows as
objects are added to the array. Another difference is that ordinary
arrays represent ordered object; however, the ordering of the
elements of an `Assoc_Type' object is unspecified.
An Assoc_Type object whose elements are of some data-type
`d' may be created using using
A = Assoc_Type[d];
For example,
A = Assoc_Type[Int_Type];
will create an associative array of integers. To create an
associative array capable of storing an arbitrary type, use the form
A = Assoc_Type[];
An optional parameter may be used to specify a default value for
array elements. For example,
A = Assoc_Type[Int_Type, -1];
creates an integer-valued associative array with a default element
value of -1. Then `A["foo"]' will return -1 if the key
`"foo"' does not exist in the array. Default values are
available only if the type was specified when the associative array
was created.
The following functions may be used with associative arrays:
assoc_get_keys
assoc_get_values
assoc_key_exists
assoc_delete_key
The `length' function may be used to obtain the number of
elements in the array.
The `foreach' construct may be used with associative arrays via
on of the following forms:
foreach k,v (A) {...}
foreach k (A) using ("keys") { ... }
foreach v (A) using ("values") { ... }
foreach k,v (A) using ("keys", "values") { ... }
In all the above forms, the loop is over all elements of the array
such that `v=A[k]'.
SEE ALSO
List_Type, Array_Type, Struct_Type
--------------------------------------------------------------
List_Type
SYNOPSIS
A list object
DESCRIPTION
An object of type `List_Type' represents a list, which is
defined as an ordered heterogeneous collection of objects.
A list may be created using, e.g.,
empty_list = {};
list_with_4_items = {[1:10], "three", 9, {1,2,3}};
Note that the last item of the list in the last example is also a
list. A List_Type object may be manipulated by the following
functions:
list_new
list_insert
list_append
list_delete
list_reverse
list_pop
A `List_Type' object may be indexed using an array syntax with
the first item on the list given by an index of 0. The
`length' function may be used to obtain the number of elements
in the list.
A copy of the list may be created using the @ operator, e.g.,
`copy = @list'.
The `foreach' statement may be used with a List_Type
object to loop over its elements:
foreach elem (list) {....}
SEE ALSO
Array_Type, Assoc_Type, Struct_Type
--------------------------------------------------------------
String_Type
SYNOPSIS
A string object
DESCRIPTION
An object of type `String_Type' represents a string of bytes or
characters, which in general have different semantics depending upon
the UTF-8 mode.
The string obeys byte-semantics when indexed as an
array. That is, `S[0]' will return the first byte of the
string `S'. For character semantics, the nth character in the
string may be obtained using `substr' function.
The `foreach' statement may be used with a String_Type
object `S' to loop over its bytes:
foreach b (S) {....}
foreach b (S) using ("bytes") {....}
To loop over its characters, the following form may be used:
foreach c (S) using ("chars") {...}
When UTF-8 mode is not in effect, the byte and character forms will
produce the same sequence. Otherwise, the string will be decoded
to generate the (wide) character sequence. If the string contains
an invalid UTF-8 encoded character, sucessive bytes of the invalid
sequence will be returned as negative integers. For example,
`"a\xAB\x{AB}"' specifies a string composed of the character
`a', a byte `0xAB', and the character `0xAB'. In
this case,
foreach c ("a\xAB\x{AB}") {...}
will produce the integer-valued sequence `'a', -0xAB, 0xAB'.
SEE ALSO
Array_Type, _slang_utf8_ok
--------------------------------------------------------------
Struct_Type
SYNOPSIS
A structure datatype
DESCRIPTION
A Struct_Type object with fields `f1', `f2',...,
`fN' may be created using
s = struct { f1, f2, ..., fN };
The fields may be accessed via the "dot" operator, e.g.,
s.f1 = 3;
if (s12.f1 == 4) s.f1++;
By default, all fields will be initialized to NULL.
A structure may also be created using the dereference operator (@):
s = @Struct_Type ("f1", "f2", ..., "fN");
s = @Struct_Type ( ["f1", "f2", ..., "fN"] );
Functions for manipulating structure fields include:
_push_struct_field_values
get_struct_field
get_struct_field_names
set_struct_field
set_struct_fields
The `foreach' loop may be used to loop over elements of a linked
list. Suppose that first structure in the list is called
`root', and that the `child' field is used to form the
chain. Then one may walk the list using:
foreach s (root) using ("child")
{
% s will take on successive values in the list
.
.
}
The loop will terminate when the last elements `child' field is
NULL. If no ``linking'' field is specified, the field name will
default to `next'.
User-defined data types are similar to the `Struct_Type'. A
type, e.g., `Vector_Type' may be created using:
typedef struct { x, y, z } Vector_Type;
Objects of this type may be created via the @ operator, e.g.,
v = @Vector_Type;
It is recommended that this be used in a function for creating such
types, e.g.,
define vector (x, y, z)
{
variable v = @Vector_Type;
v.x = x;
v.y = y;
v.z = z;
return v;
}
The action of the binary and unary operators may be defined for such
types. Consider the "+" operator. First define a function for
adding two `Vector_Type' objects:
static define vector_add (v1, v2)
{
return vector (v1.x+v2.x, v1.y+v2.y, v1.z, v2.z);
}
Then use
__add_binary ("+", Vector_Type, &vector_add, Vector_Type, Vector_Type);
to indicate that the function is to be called whenever the "+"
binary operation between two `Vector_Type' objects takes place,
e.g.,
V1 = vector (1, 2, 3);
V2 = vector (8, 9, 1);
V3 = V1 + V2;
will assigned the vector (9, 11, 4) to `V3'. Similarly, the
`"*"' operator between scalars and vectors may be defined using:
static define vector_scalar_mul (v, a)
{
return vector (a*v.x, a*v.y, a*v.z);
}
static define scalar_vector_mul (a, v)
{
return vector_scalar_mul (v, a);
}
__add_binary ("*", Vector_Type, &scalar_vector_mul, Any_Type, Vector_Type);
__add_binary ("*", Vector_Type, &vector_scalar_mul, Vector_Type, Any_Type);
Related functions include:
__add_unary
__add_string
__add_destroy
SEE ALSO
List_Type, Assoc_Type
--------------------------------------------------------------
_bofeof_info
SYNOPSIS
Control the generation of function callback code
USAGE
Int_Type _bofeof_info
DESCRIPTION
This value of this variable dictates whether or not the S-Lang
interpeter will generate code to call the beginning and end of
function callback handlers. The value of this variable is local to
the compilation unit, but is inherited by other units loaded by the
current unit.
If the value of this variable is 1 when a function is defined, then
when the function is executed, the callback handlers defined via
`_set_bof_handler' and `_set_eof_handler' will be called.
SEE ALSO
_set_bof_handler, _set_eof_handler, _boseos_info
--------------------------------------------------------------
_boseos_info
SYNOPSIS
Control the generation of BOS/EOS callback code
USAGE
Int_Type _boseos_info
DESCRIPTION
This value of this variable dictates whether or not the S-Lang
interpeter will generate code to call the beginning and end of
statement callback handlers. The value of this variable is local to
the compilation unit, but is inherited by other units loaded by the
current unit.
The value of `_boseos_info' controls the generation of code for
callbacks as follows:
Value Description
-----------------------------------------------------------------
0 No code for making callbacks will be produced.
1 Callback generation will take place for all non-branching
and looping statements.
2 Same as for 1 with the addition that code will also be
generated for branching statements (if, !if, loop, ...)
3 Same as 2, but also including break and continue
statements.
A non-branching statement is one that does not effect chain of
execution. Branching statements include all looping statements,
conditional statement, `break', `continue', and `return'.
EXAMPLE
Consider the following:
_boseos_info = 1;
define foo ()
{
if (some_expression)
some_statement;
}
_boseos_info = 2;
define bar ()
{
if (some_expression)
some_statement;
}
The function `foo' will be compiled with code generated to call the
BOS and EOS handlers when `some_statement' is executed. The
function `bar' will be compiled with code to call the handlers
for both `some_expression' and `some_statement'.
NOTES
The `sldb' debugger and `slsh''s `stkcheck.sl' make use of this
facility.
SEE ALSO
_set_bos_handler, _set_eos_handler, _bofeof_info
--------------------------------------------------------------
_clear_error
SYNOPSIS
Clear an error condition (deprecated)
USAGE
_clear_error ()
DESCRIPTION
This function has been deprecated. New code should make use of
try-catch exception handling.
This function may be used in error-blocks to clear the error that
triggered execution of the error block. Execution resumes following
the statement, in the scope of the error-block, that triggered the
error.
EXAMPLE
Consider the following wrapper around the `putenv' function:
define try_putenv (name, value)
{
variable status;
ERROR_BLOCK
{
_clear_error ();
status = -1;
}
status = 0;
putenv (sprintf ("%s=%s", name, value);
return status;
}
If `putenv' fails, it generates an error condition, which the
`try_putenv' function catches and clears. Thus `try_putenv'
is a function that returns -1 upon failure and 0 upon
success.
SEE ALSO
_trace_function, _slangtrace, _traceback
--------------------------------------------------------------
_set_bof_handler
SYNOPSIS
Set the beginning of function callback handler
USAGE
_set_bof_handler (Ref_Type func)
DESCRIPTION
This function is used to set the function to be called prior to the
execution of the body S-Lang function but after its arguments have
been evaluated, provided that function was defined
with `_bofeof_info' set appropriately. The callback function
must be defined to take a single parameter representing the name of
the function and must return nothing.
EXAMPLE
private define bof_handler (fun)
{
() = fputs ("About to execute $fun"$, stdout);
}
_set_bos_handler (&bof_handler);
NOTES
SEE ALSO
_set_eof_handler, _boseos_info, _set_bos_handler
--------------------------------------------------------------
_set_bos_handler
SYNOPSIS
Set the beginning of statement callback handler
USAGE
_set_bos_handler (Ref_Type func)
DESCRIPTION
This function is used to set the function to be called prior to the
beginning of a statement. The function will be passed two
parameters: the name of the file and the line number of the statement
to be executed. It should return nothing.
EXAMPLE
private define bos_handler (file, line)
{
() = fputs ("About to execute $file:$line\n"$, stdout);
}
_set_bos_handler (&bos_handler);
NOTES
The beginning and end of statement handlers will be called for
statements in a file only if that file was compiled with the variable
`_boseos_info' set to a non-zero value.
SEE ALSO
_set_eos_handler, _boseos_info, _bofeof_info
--------------------------------------------------------------
_set_eof_handler
SYNOPSIS
Set the beginning of function callback handler
USAGE
_set_eof_handler (Ref_Type func)
DESCRIPTION
This function is used to set the function to be called at the end of
execution of a S-Lang function, provided that function was compiled with
`_bofeof_info' set accordingly.
The callback function will be passed no parameters and it must return
nothing.
EXAMPLE
private define eof_handler ()
{
() = fputs ("Done executing the function\n", stdout);
}
_set_eof_handler (&eof_handler);
SEE ALSO
_set_bof_handler, _bofeof_info, _boseos_info
--------------------------------------------------------------
_set_eos_handler
SYNOPSIS
Set the end of statement callback handler
USAGE
_set_eos_handler (Ref_Type func)
DESCRIPTION
This function is used to set the function to be called at the end of
a statement. The function will be passed no parameters and it should
return nothing.
EXAMPLE
private define eos_handler ()
{
() = fputs ("Done executing the statement\n", stdout);
}
_set_eos_handler (&eos_handler);
NOTES
The beginning and end of statement handlers will be called for
statements in a file only if that file was compiled with the variable
`_boseos_info' set to a non-zero value.
SEE ALSO
_set_bos_handler, _boseos_info, _bofeof_info
--------------------------------------------------------------
_slangtrace
SYNOPSIS
Turn function tracing on or off
USAGE
Integer_Type _slangtrace
DESCRIPTION
The `_slangtrace' variable is a debugging aid that when set to a
non-zero value enables tracing when function declared by
`_trace_function' is entered. If the value is greater than
zero, both intrinsic and user defined functions will get traced.
However, if set to a value less than zero, intrinsic functions will
not get traced.
SEE ALSO
_trace_function, _traceback, _print_stack
--------------------------------------------------------------
_traceback
SYNOPSIS
Generate a traceback upon error
USAGE
Integer_Type _traceback
DESCRIPTION
`_traceback' is an intrinsic integer variable whose bitmapped value
controls the generation of the call-stack traceback upon error.
When set to 0, no traceback will be generated. Otherwise its value
is the bitwise-or of the following integers:
1 Create a full traceback
2 Omit local variable information
4 Generate just one line of traceback
The default value of this variable is 4.
NOTES
Running `slsh' with the `-g' option causes this variable to be
set to 1.
SEE ALSO
_boseos_info
--------------------------------------------------------------
_trace_function
SYNOPSIS
Set the function to trace
USAGE
_trace_function (String_Type f)
DESCRIPTION
`_trace_function' declares that the S-Lang function with name
`f' is to be traced when it is called. Calling
`_trace_function' does not in itself turn tracing on. Tracing
is turned on only when the variable `_slangtrace' is non-zero.
SEE ALSO
_slangtrace, _traceback
--------------------------------------------------------------
chdir
SYNOPSIS
Change the current working directory
USAGE
Int_Type chdir (String_Type dir)
DESCRIPTION
The `chdir' function may be used to change the current working
directory to the directory specified by `dir'. Upon success it
returns zero. Upon failure it returns `-1' and sets
`errno' accordingly.
SEE ALSO
mkdir, stat_file
--------------------------------------------------------------
chmod
SYNOPSIS
Change the mode of a file
USAGE
Int_Type chmod (String_Type file, Int_Type mode)
DESCRIPTION
The `chmod' function changes the permissions of the specified
file to those given by `mode'. It returns `0' upon
success, or `-1' upon failure setting `errno' accordingly.
See the system specific documentation for the C library
function `chmod' for a discussion of the `mode' parameter.
SEE ALSO
chown, stat_file
--------------------------------------------------------------
chown
SYNOPSIS
Change the owner of a file
USAGE
Int_Type chown (String_Type file, Int_Type uid, Int_Type gid)
DESCRIPTION
The `chown' function is used to change the user-id and group-id of
`file' to `uid' and `gid', respectively. It returns
0 upon success and -1 upon failure, with `errno'
set accordingly.
NOTES
On most systems, only the superuser can change the ownership of a
file.
Some systems do not support this function.
SEE ALSO
chmod, stat_file
--------------------------------------------------------------
getcwd
SYNOPSIS
Get the current working directory
USAGE
String_Type getcwd ()
DESCRIPTION
The `getcwd' function returns the absolute pathname of the
current working directory. If an error occurs or it cannot
determine the working directory, it returns NULL and sets
`errno' accordingly.
NOTES
Under Unix, OS/2, and MSDOS, the pathname returned by this function
includes the trailing slash character. It may also include
the drive specifier for systems where that is meaningful.
SEE ALSO
mkdir, chdir, errno
--------------------------------------------------------------
hardlink
SYNOPSIS
Create a hard-link
USAGE
Int_Type hardlink (String_Type oldpath, String_Type newpath)
DESCRIPTION
The `hardlink' function creates a hard-link called
`newpath' to the existing file `oldpath'. If the link was
sucessfully created, the function will return 0. Upon error, the
function returns -1 and sets `errno' accordingly.
NOTES
Not all systems support the concept of a hard-link.
SEE ALSO
symlink
--------------------------------------------------------------
listdir
SYNOPSIS
Get a list of the files in a directory
USAGE
String_Type[] listdir (String_Type dir)
DESCRIPTION
The `listdir' function returns the directory listing of all the
files in the specified directory `dir' as an array of strings.
It does not return the special files `".."' and `"."' as
part of the list.
SEE ALSO
stat_file, stat_is, length
--------------------------------------------------------------
lstat_file
SYNOPSIS
Get information about a symbolic link
USAGE
Struct_Type lstat_file (String_Type file)
DESCRIPTION
The `lstat_file' function behaves identically to `stat_file'
but if `file' is a symbolic link, `lstat_file' returns
information about the link itself, and not the file that it
references.
See the documentation for `stat_file' for more information.
NOTES
On systems that do not support symbolic links, there is no
difference between this function and the `stat_file' function.
SEE ALSO
stat_file, readlink
--------------------------------------------------------------
mkdir
SYNOPSIS
Create a new directory
USAGE
Int_Type mkdir (String_Type dir [,Int_Type mode])
DESCRIPTION
The `mkdir' function creates a directory whose name is specified
by the `dir' parameter with permissions given by the optional
`mode' parameter. Upon success `mkdir' returns 0, or it
returns `-1' upon failure setting `errno' accordingly. In
particular, if the directory already exists, the function will fail
and set errno to EEXIST.
EXAMPLE
define my_mkdir (dir)
{
if (0 == mkdir (dir)) return;
if (errno == EEXIST) return;
throw IOError,
sprintf ("mkdir %s failed: %s", dir, errno_string (errno));
}
NOTES
The `mode' parameter may not be meaningful on all systems. On
systems where it is meaningful, the actual permissions on the newly
created directory are modified by the process's umask.
SEE ALSO
rmdir, getcwd, chdir, fopen, errno
--------------------------------------------------------------
readlink
SYNOPSIS
String_Type readlink (String_Type path)
USAGE
Get the value of a symbolic link
DESCRIPTION
The `readlink' function returns the value of a symbolic link.
Upon failure, NULL is returned and `errno' set accordingly.
NOTES
Not all systems support this function.
SEE ALSO
symlink, lstat_file, stat_file, stat_is
--------------------------------------------------------------
remove
SYNOPSIS
Delete a file
USAGE
Int_Type remove (String_Type file)
DESCRIPTION
The `remove' function deletes a file. It returns 0 upon
success, or -1 upon error and sets `errno' accordingly.
SEE ALSO
rename, rmdir
--------------------------------------------------------------
rename
SYNOPSIS
Rename a file
USAGE
Int_Type rename (String_Type old, String_Type new)
DESCRIPTION
The `rename' function renames a file from `old' to `new'
moving it between directories if necessary. This function may fail
if the directories are not on the same file system. It returns
0 upon success, or -1 upon error and sets `errno' accordingly.
SEE ALSO
remove, errno
--------------------------------------------------------------
rmdir
SYNOPSIS
Remove a directory
USAGE
Int_Type rmdir (String_Type dir)
DESCRIPTION
The `rmdir' function deletes the specified directory. It returns
0 upon success or -1 upon error and sets `errno' accordingly.
NOTES
The directory must be empty before it can be removed.
SEE ALSO
rename, remove, mkdir
--------------------------------------------------------------
stat_file
SYNOPSIS
Get information about a file
USAGE
Struct_Type stat_file (String_Type file)
DESCRIPTION
The `stat_file' function returns information about `file'
through the use of the system `stat' call. If the stat call
fails, the function returns NULL and sets errno accordingly.
If it is successful, it returns a stat structure with the following
integer-value fields:
st_dev
st_ino
st_mode
st_nlink
st_uid
st_gid
st_rdev
st_size
st_atime
st_mtime
st_ctime
See the C library documentation of `stat' for a discussion of the
meanings of these fields.
EXAMPLE
The following example shows how the `stat_file' function may be
used to get the size of a file:
define file_size (file)
{
variable st;
st = stat_file(file);
if (st == NULL)
throw IOError, "Unable to stat $file"$;
return st.st_size;
}
SEE ALSO
lstat_file, stat_is
--------------------------------------------------------------
stat_is
SYNOPSIS
Parse the st_mode field of a stat structure
USAGE
Char_Type stat_is (String_Type type, Int_Type st_mode)
DESCRIPTION
The `stat_is' function returns a boolean value according to
whether or not the `st_mode' parameter is of the specified type.
Specifically, `type' must be one of the strings:
"sock" (socket)
"fifo" (fifo)
"blk" (block device)
"chr" (character device)
"reg" (regular file)
"lnk" (link)
"dir" (dir)
It returns a non-zero value if `st_mode' corresponds to
`type'.
EXAMPLE
The following example illustrates how to use the `stat_is'
function to determine whether or not a file is a directory:
define is_directory (file)
{
variable st;
st = stat_file (file);
if (st == NULL) return 0;
return stat_is ("dir", st.st_mode);
}
SEE ALSO
stat_file, lstat_file
--------------------------------------------------------------
symlink
SYNOPSIS
Create a symbolic link
USAGE
status = symlink (String_Type oldpath, String_Type new_path)
DESCRIPTION
The `symlink' function may be used to create a symbolic link
named `new_path' for `oldpath'. If successful, the function
returns 0, otherwise it returns -1 and sets `errno' appropriately.
NOTES
This function is not supported on all systems and even if supported,
not all file systems support the concept of a symbolic link.
SEE ALSO
readlink, hardlink
--------------------------------------------------------------
_$
SYNOPSIS
Expand the dollar-escaped variables in a string
USAGE
String_Type _$(String_Type s)
DESCRIPTION
This function expands the dollar-escaped variables in a string and
returns the resulting string.
EXAMPLE
Consider the following code fragment:
private variable Format = "/tmp/foo-$time.$pid";
define make_filename ()
{
variable pid = getpid ();
variable time = _time ();
return _$(Format);
}
Note that the variable `Format' contains dollar-escaped
variables, but because the `$' suffix was omitted from the
string literal, the variables are not expanded. Instead expansion is
deferred until execution of the `make_filename' function through
the use of the `_$' function.
SEE ALSO
eval, getenv
--------------------------------------------------------------
autoload
SYNOPSIS
Load a function from a file
USAGE
autoload (String_Type funct, String_Type file)
DESCRIPTION
The `autoload' function is used to declare `funct' to the
interpreter and indicate that it should be loaded from `file'
when it is actually used. If `func' contains a namespace
prefix, then the file will be loaded into the corresponding
namespace. Otherwise, if the `autoload' function is called
from an execution namespace that is not the Global namespace nor an
anonymous namespace, then the file will be loaded into the execution
namespace.
EXAMPLE
Suppose `bessel_j0' is a function defined in the file
`bessel.sl'. Then the statement
autoload ("bessel_j0", "bessel.sl");
will cause `bessel.sl' to be loaded prior to the execution of
`bessel_j0'.
SEE ALSO
evalfile, import
--------------------------------------------------------------
byte_compile_file
SYNOPSIS
Compile a file to byte-code for faster loading.
USAGE
byte_compile_file (String_Type file, Int_Type method)
DESCRIPTION
The `byte_compile_file' function byte-compiles `file'
producing a new file with the same name except a `'c'' is added
to the output file name. For example, `file' is
`"site.sl"', then this function produces a new file named
`site.slc'.
NOTES
The `method' parameter is not used in the current
implementation, but may be in the future. For now, set
it to `0'.
SEE ALSO
evalfile
--------------------------------------------------------------
eval
SYNOPSIS
Interpret a string as S-Lang code
USAGE
eval (String_Type expression [,String_Type namespace])
DESCRIPTION
The `eval' function parses a string as S-Lang code and executes the
result. If called with the optional namespace argument, then the
string will be evaluated in the specified namespace. If that
namespace does not exist it will be created first.
This is a useful function in many contexts including those where
it is necessary to dynamically generate function definitions.
EXAMPLE
if (0 == is_defined ("my_function"))
eval ("define my_function () { message (\"my_function\"); }");
SEE ALSO
is_defined, autoload, evalfile
--------------------------------------------------------------
evalfile
SYNOPSIS
Interpret a file containing S-Lang code
USAGE
Int_Type evalfile (String_Type file [,String_Type namespace])
DESCRIPTION
The `evalfile' function loads `file' into the interpreter
and executes it. If called with the optional namespace argument,
the file will be loaded into the specified namespace, which will be
created if necessary. If given no namespace argument and the file
has already been loaded, then it will be loaded again into an
anonymous namespace. A namespace argument given by the empty string
will also cause the file to be loaded into a new anonymous namespace.
If no errors were encountered, 1 will be returned; otherwise,
a S-Lang exception will be thrown and the function will return zero.
EXAMPLE
define load_file (file)
{
try
{
() = evalfile (file);
}
catch AnyError;
}
NOTES
For historical reasons, the return value of this function is not
really useful.
The file is searched along an application-defined load-path. The
`get_slang_load_path' and `set_slang_load_path' functions
may be used to set and query the path.
SEE ALSO
eval, autoload, set_slang_load_path, get_slang_load_path
--------------------------------------------------------------
get_slang_load_path
SYNOPSIS
Get the value of the interpreter's load-path
USAGE
String_Type get_slang_load_path ()
DESCRIPTION
This function retrieves the value of the delimiter-separated search
path used for loading files. The delimiter is OS-specific and may
be queried using the `path_get_delimiter' function.
NOTES
Some applications may not support the built-in load-path searching
facility provided by the underlying library.
SEE ALSO
set_slang_load_path, path_get_delimiter
--------------------------------------------------------------
set_slang_load_path
SYNOPSIS
Set the value of the interpreter's load-path
USAGE
set_slang_load_path (String_Type path)
DESCRIPTION
This function may be used to set the value of the
delimiter-separated search path used by the `evalfile' and
`autoload' functions for locating files. The delimiter is
OS-specific and may be queried using the `path_get_delimiter'
function.
EXAMPLE
public define prepend_to_slang_load_path (p)
{
variable s = stat_file (p);
if (s == NULL) return;
if (0 == stat_is ("dir", s.st_mode))
return;
p = sprintf ("%s%c%s", p, path_get_delimiter (), get_slang_load_path ());
set_slang_load_path (p);
}
NOTES
Some applications may not support the built-in load-path searching
facility provided by the underlying library.
SEE ALSO
get_slang_load_path, path_get_delimiter, evalfile, autoload
--------------------------------------------------------------
get_import_module_path
SYNOPSIS
Get the search path for dynamically loadable objects
USAGE
String_Type get_import_module_path ()
DESCRIPTION
The `get_import_module_path' may be used to get the search path
for dynamically shared objects. Such objects may be made accessible
to the application via the `import' function.
SEE ALSO
import, set_import_module_path
--------------------------------------------------------------
import
SYNOPSIS
Dynamically link to a specified module
USAGE
import (String_Type module [, String_Type namespace])
DESCRIPTION
The `import' function causes the run-time linker to dynamically
link to the shared object specified by the `module' parameter.
It searches for the shared object as follows: First a search is
performed along all module paths specified by the application. Then
a search is made along the paths defined via the
`set_import_module_path' function. If not found, a search is
performed along the paths given by the `SLANG_MODULE_PATH'
environment variable. Finally, a system dependent search is
performed (e.g., using the `LD_LIBRARY_PATH' environment
variable).
The optional second parameter may be used to specify a namespace
for the intrinsic functions and variables of the module. If this
parameter is not present, the intrinsic objects will be placed into
the active namespace, or global namespace if the active namespace is
anonymous.
This function throws an `ImportError' if the specified module is
not found.
NOTES
The `import' function is not available on all systems.
SEE ALSO
set_import_module_path, use_namespace, current_namespace, getenv, evalfile
--------------------------------------------------------------
set_import_module_path
SYNOPSIS
Set the search path for dynamically loadable objects
USAGE
set_import_module_path (String_Type path_list)
DESCRIPTION
The `set_import_module_path' may be used to set the search path
for dynamically shared objects. Such objects may be made accessible
to the application via the `import' function.
The actual syntax for the specification of the set of paths will
vary according to the operating system. Under Unix, a colon
character is used to separate paths in `path_list'. For win32
systems a semi-colon is used. The `path_get_delimiter'
function may be used to get the value of the delimiter.
SEE ALSO
import, get_import_module_path, path_get_delimiter
--------------------------------------------------------------
add_doc_file
SYNOPSIS
Make a documentation file known to the help system
USAGE
add_doc_file (String_Type file)
DESCRIPTION
The `add_doc_file' is used to add a documentation file to the
system. Such files are searched by the
`get_doc_string_from_file' function. The `file' must be
specified using the full path.
SEE ALSO
set_doc_files, get_doc_files, get_doc_string_from_file
--------------------------------------------------------------
_apropos
SYNOPSIS
Generate a list of functions and variables
USAGE
Array_Type _apropos (String_Type ns, String_Type s, Integer_Type flags)
DESCRIPTION
The `_apropos' function may be used to get a list of all defined
objects in the namespace `ns' whose name matches the regular
expression `s' and whose type matches those specified by
`flags'. It returns an array of strings containing the names
matched.
The second parameter `flags' is a bit mapped value whose bits
are defined according to the following table
1 Intrinsic Function
2 User-defined Function
4 Intrinsic Variable
8 User-defined Variable
EXAMPLE
define apropos (s)
{
variable n, name, a;
a = _apropos ("Global", s, 0xF);
vmessage ("Found %d matches:", length (a));
foreach name (a)
message (name);
}
prints a list of all matches.
NOTES
If the namespace specifier `ns' is the empty string `""',
then the namespace will default to the static namespace of the
current compilation unit.
SEE ALSO
is_defined, sprintf, _get_namespaces
--------------------------------------------------------------
_function_name
SYNOPSIS
Returns the name of the currently executing function
USAGE
String_Type _function_name ()
DESCRIPTION
This function returns the name of the currently executing function.
If called from top-level, it returns the empty string.
SEE ALSO
_trace_function, is_defined
--------------------------------------------------------------
__get_defined_symbols
SYNOPSIS
Get the symbols defined by the preprocessor
USAGE
Int_Type __get_defined_symbols ()
DESCRIPTION
The `__get_defined_symbols' functions is used to get the list of
all the symbols defined by the S-Lang preprocessor. It pushes each
of the symbols on the stack followed by the number of items pushed.
SEE ALSO
is_defined, _apropos, _get_namespaces
--------------------------------------------------------------
get_doc_files
SYNOPSIS
Get the list of documentation files
USAGE
String_Type[] = get_doc_files ()
DESCRIPTION
The `get_doc_files' function returns the internal list of
documentation files as an array of strings.
SEE ALSO
set_doc_files, add_doc_file, get_doc_string_from_file
--------------------------------------------------------------
get_doc_string_from_file
SYNOPSIS
Read documentation from a file
USAGE
String_Type get_doc_string_from_file ([String_Type f,] String_Type t)
DESCRIPTION
If called with two arguments, `get_doc_string_from_file' opens
the documentation file `f' and searches it for topic `t'.
Otherwise, it will search an internal list of documentation files
looking for the documentation associated with the topic `t'. If
found, the documentation for `t' will be returned, otherwise the
function will return NULL.
Files may be added to the internal list via the `add_doc_file'
or `set_doc_files' functions.
SEE ALSO
add_doc_file, set_doc_files, get_doc_files, _slang_doc_dir
--------------------------------------------------------------
_get_namespaces
SYNOPSIS
Returns a list of namespace names
USAGE
String_Type[] _get_namespaces ()
DESCRIPTION
This function returns a string array containing the names of the
currently defined namespaces.
SEE ALSO
_apropos, use_namespace, implements, __get_defined_symbols
--------------------------------------------------------------
is_defined
SYNOPSIS
Determine if a variable or function is defined
USAGE
Integer_Type is_defined (String_Type name)
DESCRIPTION
This function is used to determine whether or not a function or
variable of the given name has been defined. If the specified name
has not been defined, the function returns 0. Otherwise, it
returns a non-zero value that depends on the type of object
attached to the name. Specifically, it returns one of the following
values:
+1 intrinsic function
+2 slang function
-1 intrinsic variable
-2 slang variable
0 undefined
EXAMPLE
Consider the function:
define runhooks (hook)
{
if (2 == is_defined(hook)) eval(hook);
}
This function could be called from another S-Lang function to
allow customization of that function, e.g., if the function
represents a mode, the hook could be called to setup keybindings
for the mode.
SEE ALSO
typeof, eval, autoload, __get_reference, __is_initialized
--------------------------------------------------------------
__is_initialized
SYNOPSIS
Determine whether or not a variable has a value
USAGE
Integer_Type __is_initialized (Ref_Type r)
DESCRIPTION
This function returns non-zero of the object referenced by `r'
is initialized, i.e., whether it has a value. It returns 0 if the
referenced object has not been initialized.
EXAMPLE
The function:
define zero ()
{
variable f;
return __is_initialized (&f);
}
will always return zero, but
define one ()
{
variable f = 0;
return __is_initialized (&f);
}
will return one.
SEE ALSO
__get_reference, __uninitialize, is_defined, typeof, eval
--------------------------------------------------------------
_NARGS
SYNOPSIS
The number of parameters passed to a function
USAGE
Integer_Type _NARGS
The value of the `_NARGS' variable represents the number of
arguments passed to the function. This variable is local to each
function.
EXAMPLE
This example uses the `_NARGS' variable to print the list of
values passed to the function:
define print_values ()
{
variable arg;
if (_NARGS == 0)
{
message ("Nothing to print");
return;
}
foreach arg (__pop_args (_NARGS))
vmessage ("Argument value is: %S", arg.value);
}
SEE ALSO
__pop_args, __push_args, typeof
--------------------------------------------------------------
set_doc_files
SYNOPSIS
Set the internal list of documentation files
USAGE
set_doc_files (String_Type[] list)
DESCRIPTION
The `set_doc_files' function may be used to set the internal
list of documentation files. It takes a single parameter, which is
required to be an array of strings. The internal file list is set
to the files specified by the elements of the array.
EXAMPLE
The following example shows how to add all the files in a specified
directory to the internal list. It makes use of the `glob'
function that is distributed as part of `slsh'.
files = glob ("/path/to/doc/files/*.sld");
set_doc_files ([files, get_doc_files ()]);
SEE ALSO
get_doc_files, add_doc_file, get_doc_string_from_file
--------------------------------------------------------------
_slang_doc_dir
SYNOPSIS
Installed documentation directory
USAGE
String_Type _slang_doc_dir
DESCRIPTION
The `_slang_doc_dir' variable is a read-only variable that
specifies the compile-time installation location of the S-Lang
documentation.
SEE ALSO
get_doc_string_from_file
--------------------------------------------------------------
_slang_version
SYNOPSIS
The S-Lang library version number
USAGE
Integer_Type _slang_version
DESCRIPTION
`_slang_version' is a read-only variable that gives the version
number of the S-Lang library.
SEE ALSO
_slang_version_string
--------------------------------------------------------------
_slang_version_string
SYNOPSIS
The S-Lang library version number as a string
USAGE
String_Type _slang_version_string
DESCRIPTION
`_slang_version_string' is a read-only variable that gives a
string representation of the version number of the S-Lang library.
SEE ALSO
_slang_version
--------------------------------------------------------------
list_append
SYNOPSIS
Append an object to a list
USAGE
list_append (List_Type list, object [,Int_Type nth])
DESCRIPTION
The `list_append' function is like `list_insert' except
this function appends the object to the the list. The optional
argument `nth' may be used to specify where the object is to be
appended. See the documentation on `list_insert' for more details.
SEE ALSO
list_insert, list_delete, list_pop, list_new, list_reverse
--------------------------------------------------------------
list_delete
SYNOPSIS
Remove an item from a list
USAGE
list_delete (List_Type list, Int_Type nth)
DESCRIPTION
This function removes the `nth' item in the specified list.
The first item in the list corresponds to a value of `nth'
equal to zero. If `nth' is negative, then the indexing is with
respect to the end of the list with the last item corresponding to
`nth' equal to -1.
SEE ALSO
list_insert, list_append, list_pop, list_new, list_reverse
--------------------------------------------------------------
list_insert
SYNOPSIS
Insert an item into a list
USAGE
list_insert (List_Type list, object [,Int_Type nth])
DESCRIPTION
This function may be used to insert an object into the specified
list. With just two arguments, the object will be inserted at the
beginning of the list. The optional third argument, `nth', may
be used to specify the insertion point. The first item in the list
corresponds to a value of `nth' equal to zero. If `nth'
is negative, then the indexing is with respect to the end of the
list with the last item given by a value of `nth' equal to -1.
NOTES
It is important to note that
list_insert (list, object, 0);
is not the same as
list = {object, list}
since the latter creates a new list with two items, `object'
and the old list.
SEE ALSO
list_append, list_pop, list_delete, list_new, list_reverse
--------------------------------------------------------------
list_new
SYNOPSIS
Create a new list
USAGE
List_Type list_new ()
DESCRIPTION
This function creates a new empty List_Type object. Such a
list may also be created using the syntax
list = {};
SEE ALSO
list_delete, list_insert, list_append, list_reverse, list_pop
--------------------------------------------------------------
list_pop
SYNOPSIS
Extract an item from a list
USAGE
object = list_pop (List_Type list [, Int_Type nth])
DESCRIPTION
The `list_pop' function returns a object from a list deleting
the item from the list in the process. If the second argument is
present, then it may be used to specify the position in the list
where the item is to be obtained. If called with a single argument,
the first item in the list will be used.
SEE ALSO
list_delete, list_insert, list_append, list_reverse, list_new
--------------------------------------------------------------
list_reverse
SYNOPSIS
Reverse a list
USAGE
list_reverse (List_Type list)
DESCRIPTION
This function may be used to reverse the items in list.
NOTES
This function does not create a new list. The list passed to the
function will be reversed upon return from the function. If it is
desired to create a separate reversed list, then a separate copy
should be made, e.g.,
rev_list = @list;
list_reverse (rev_list);
SEE ALSO
list_new, list_insert, list_append, list_delete, list_pop
--------------------------------------------------------------
abs
SYNOPSIS
Compute the absolute value of a number
USAGE
y = abs(x)
DESCRIPTION
The `abs' function returns the absolute value of an arithmetic
type. If its argument is a complex number (Complex_Type),
then it returns the modulus. If the argument is an array, a new
array will be created whose elements are obtained from the original
array by using the `abs' function.
SEE ALSO
sign, sqr
--------------------------------------------------------------
acos
SYNOPSIS
Compute the arc-cosine of a number
USAGE
y = acos (x)
DESCRIPTION
The `acos' function computes the arc-cosine of a number and
returns the result. If its argument is an array, the
`acos' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
acosh
SYNOPSIS
Compute the inverse cosh of a number
USAGE
y = acosh (x)
DESCRIPTION
The `acosh' function computes the inverse hyperbolic cosine of a number and
returns the result. If its argument is an array, the
`acosh' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
asin
SYNOPSIS
Compute the arc-sine of a number
USAGE
y = asin (x)
DESCRIPTION
The `asin' function computes the arc-sine of a number and
returns the result. If its argument is an array, the
`asin' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
asinh
SYNOPSIS
Compute the inverse-sinh of a number
USAGE
y = asinh (x)
DESCRIPTION
The `asinh' function computes the inverse hyperbolic sine of a number and
returns the result. If its argument is an array, the
`asinh' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
atan
SYNOPSIS
Compute the arc-tangent of a number
USAGE
y = atan (x)
DESCRIPTION
The `atan' function computes the arc-tangent of a number and
returns the result. If its argument is an array, the
`atan' function will be applied to each element and the result returned
as an array.
SEE ALSO
atan2, cos, acosh, cosh
--------------------------------------------------------------
atan2
SYNOPSIS
Compute the arc-tangent of the ratio of two variables
USAGE
z = atan2 (y, x)
DESCRIPTION
The `atan2' function computes the arc-tangent of the ratio
`y/x' and returns the result as a value that has the
proper sign for the quadrant where the point (x,y) is located. The
returned value `z' will satisfy (-PI < z <= PI). If either of the
arguments is an array, an array of the corresponding values will be returned.
SEE ALSO
hypot, cos, atan, acosh, cosh
--------------------------------------------------------------
atanh
SYNOPSIS
Compute the inverse-tanh of a number
USAGE
y = atanh (x)
DESCRIPTION
The `atanh' function computes the inverse hyperbolic tangent of a number and
returns the result. If its argument is an array, the
`atanh' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
ceil
SYNOPSIS
Round x up to the nearest integral value
USAGE
y = ceil (x)
DESCRIPTION
This function rounds its numeric argument up to the nearest integral
value. If the argument is an array, the corresponding array will be
returned.
SEE ALSO
floor, round
--------------------------------------------------------------
Conj
SYNOPSIS
Compute the complex conjugate of a number
USAGE
z1 = Conj (z)
DESCRIPTION
The `Conj' function returns the complex conjugate of a number.
If its argument is an array, the `Conj' function will be applied to each
element and the result returned as an array.
SEE ALSO
Real, Imag, abs
--------------------------------------------------------------
cos
SYNOPSIS
Compute the cosine of a number
USAGE
y = cos (x)
DESCRIPTION
The `cos' function computes the cosine of a number and
returns the result. If its argument is an array, the
`cos' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
cosh
SYNOPSIS
Compute the hyperbolic cosine of a number
USAGE
y = cosh (x)
DESCRIPTION
The `cosh' function computes the hyperbolic cosine of a number and
returns the result. If its argument is an array, the
`cosh' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
_diff
SYNOPSIS
Compute the absolute difference of two values
USAGE
y = _diff (x, y)
DESCRIPTION
The `_diff' function returns a floating point number equal to
the absolute value of the difference of its two arguments.
If either argument is an array, an array of the corresponding values
will be returned.
SEE ALSO
abs
--------------------------------------------------------------
exp
SYNOPSIS
Compute the exponential of a number
USAGE
y = exp (x)
DESCRIPTION
The `exp' function computes the exponential of a number and
returns the result. If its argument is an array, the
`exp' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
feqs
SYNOPSIS
Test the approximate equality of two numbers
USAGE
Char_Type feqs (a, b [,reldiff [,absdiff]]
DESCRIPTION
This function compares two floating point numbers `a' and
`b', and returns a non-zero value if they are equal to within a
specified tolerance; otherwise 0 will be returned. If either is an
array, a corresponding boolean array will be returned.
The tolerances are specified as relative and absolute differences via
the optional third and fourth arguments. If no optional arguments
are present, the tolerances default to `reldiff=0.01' and
`absdiff=1e-6'. If only the relative difference has been
specified, the absolute difference (`absdiff') will be taken to
be 0.0.
For the case when `|b|>=|a|', `a' and `b' are
considered to be equal to within the specified tolerances if either
`|b-a|<=absdiff' or `|b-a|/|b|<=reldiff' is true.
SEE ALSO
fneqs, fgteqs, flteqs
--------------------------------------------------------------
fgteqs
SYNOPSIS
Compare two numbers using specified tolerances
.
USAGE
Char_Type feqs (a, b [,reldiff [,absdiff]]
DESCRIPTION
This function is functionally equivalent to:
(a >= b) or feqs(a,b,...)
See the documentation of `feqs' for more information.
SEE ALSO
feqs, fneqs, flteqs
--------------------------------------------------------------
floor
SYNOPSIS
Round x down to the nearest integer
USAGE
y = floor (x)
DESCRIPTION
This function rounds its numeric argument down to the nearest
integral value. If the argument is an array, the corresponding array
will be returned.
SEE ALSO
ceil, round, nint
--------------------------------------------------------------
flteqs
SYNOPSIS
Compare two numbers using specified tolerances
.
USAGE
Char_Type feqs (a, b [,reldiff [,absdiff]]
DESCRIPTION
This function is functionally equivalent to:
(a <= b) or feqs(a,b,...)
See the documentation of `feqs' for more information.
SEE ALSO
feqs, fneqs, fgteqs
--------------------------------------------------------------
fneqs
SYNOPSIS
Test the approximate inequality of two numbers
USAGE
Char_Type feqs (a, b [,reldiff [,absdiff]]
DESCRIPTION
This function is functionally equivalent to:
not fneqs(a,b,...)
See the documentation of `feqs' for more information.
SEE ALSO
feqs, fgteqs, flteqs
--------------------------------------------------------------
hypot
SYNOPSIS
Compute sqrt(x^2+y^2)
USAGE
r = hypot (x, y)
DESCRIPTION
The `hypot' function computes the quantity `sqrt(x^2+y^2)'
except that it employs an algorithm that tries to avoid arithmetic
overflow when `x' or `y' are large. If either argument is
an array, an array of the corresponding values will be returned.
SEE ALSO
atan2, cos, atan, acosh, cosh
--------------------------------------------------------------
Imag
SYNOPSIS
Compute the imaginary part of a number
USAGE
i = Imag (z)
DESCRIPTION
The `Imag' function returns the imaginary part of a number.
If its argument is an array, the `Imag' function will be applied to each
element and the result returned as an array.
SEE ALSO
Real, Conj, abs
--------------------------------------------------------------
isinf
SYNOPSIS
Test for infinity
USAGE
y = isinf (x)
DESCRIPTION
This function returns 1 if x corresponds to an IEEE infinity, or 0
otherwise. If the argument is an array, an array of the
corresponding values will be returned.
SEE ALSO
isnan, _Inf
--------------------------------------------------------------
isnan
SYNOPSIS
isnan
USAGE
y = isnan (x)
DESCRIPTION
This function returns 1 if x corresponds to an IEEE NaN (Not a Number),
or 0 otherwise. If the argument is an array, an array of
the corresponding values will be returned.
SEE ALSO
isinf, _NaN
--------------------------------------------------------------
log
SYNOPSIS
Compute the logarithm of a number
USAGE
y = log (x)
DESCRIPTION
The `log' function computes the natural logarithm of a number and
returns the result. If its argument is an array, the
`log' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
log10
SYNOPSIS
Compute the base-10 logarithm of a number
USAGE
y = log10 (x)
DESCRIPTION
The `log10' function computes the base-10 logarithm of a number and
returns the result. If its argument is an array, the
`log10' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
_max
SYNOPSIS
Compute the maximum of two values
USAGE
z = _max (x,y)
DESCRIPTION
The `_max' function returns a floating point number equal to the
maximum value of its two arguments.
If either argument is an array, an array of the corresponding values
will be returned.
NOTES
This function returns a floating point result even when both
arguments are integers.
SEE ALSO
max, _min, min
--------------------------------------------------------------
_min
SYNOPSIS
Compute the minimum of two values
USAGE
z = _min (x,y)
DESCRIPTION
The `_min' function returns a floating point number equal to the
minimum value of its two arguments.
If either argument is an array, an array of the corresponding values
will be returned.
NOTES
This function returns a floating point result even when both
arguments are integers.
SEE ALSO
min, _max, max
--------------------------------------------------------------
mul2
SYNOPSIS
Multiply a number by 2
USAGE
y = mul2(x)
DESCRIPTION
The `mul2' function multiplies an arithmetic type by two and
returns the result. If its argument is an array, a new array will
be created whose elements are obtained from the original array by
using the `mul2' function.
SEE ALSO
sqr, abs
--------------------------------------------------------------
nint
SYNOPSIS
Round to the nearest integer
USAGE
i = nint(x)
DESCRIPTION
The `nint' rounds its argument to the nearest integer and
returns the result. If its argument is an array, a new array will
be created whose elements are obtained from the original array
elements by using the `nint' function.
SEE ALSO
round, floor, ceil
--------------------------------------------------------------
polynom
SYNOPSIS
Evaluate a polynomial
USAGE
Double_Type polynom(Double_Type a, b, ...c, Integer_Type n, Double_Type x)
DESCRIPTION
The `polynom' function returns the value of the polynomial expression:
ax^n + bx^(n - 1) + ... c
NOTES
The `polynom' function should be extended to work with complex
and array data types. The current implementation is limited to
Double_Type quantities.
SEE ALSO
exp
--------------------------------------------------------------
Real
SYNOPSIS
Compute the real part of a number
USAGE
r = Real (z)
DESCRIPTION
The `Real' function returns the real part of a number. If its
argument is an array, the `Real' function will be applied to
each element and the result returned as an array.
SEE ALSO
Imag, Conj, abs
--------------------------------------------------------------
round
SYNOPSIS
Round to the nearest integral value
USAGE
y = round (x)
DESCRIPTION
This function rounds its argument to the nearest integral value and
returns it as a floating point result. If the argument is an array,
an array of the corresponding values will be returned.
SEE ALSO
floor, ceil, nint
--------------------------------------------------------------
set_float_format
SYNOPSIS
Set the format for printing floating point values.
USAGE
set_float_format (String_Type fmt)
DESCRIPTION
The `set_float_format' function is used to set the floating
point format to be used when floating point numbers are printed.
The routines that use this are the traceback routines and the
`string' function, any anything based upon the `string'
function. The default value is `"%g"'
EXAMPLE
s = string (PI); % --> s = "3.14159"
set_float_format ("%16.10f");
s = string (PI); % --> s = "3.1415926536"
set_float_format ("%10.6e");
s = string (PI); % --> s = "3.141593e+00"
SEE ALSO
string, sprintf, double
--------------------------------------------------------------
sign
SYNOPSIS
Compute the sign of a number
USAGE
y = sign(x)
DESCRIPTION
The `sign' function returns the sign of an arithmetic type. If
its argument is a complex number (Complex_Type), the
`sign' will be applied to the imaginary part of the number. If
the argument is an array, a new array will be created whose elements
are obtained from the original array by using the `sign'
function.
When applied to a real number or an integer, the `sign' function
returns -1, 0, or `+1' according to whether the number is
less than zero, equal to zero, or greater than zero, respectively.
SEE ALSO
abs
--------------------------------------------------------------
sin
SYNOPSIS
Compute the sine of a number
USAGE
y = sin (x)
DESCRIPTION
The `sin' function computes the sine of a number and
returns the result. If its argument is an array, the
`sin' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
sinh
SYNOPSIS
Compute the hyperbolic sine of a number
USAGE
y = sinh (x)
DESCRIPTION
The `sinh' function computes the hyperbolic sine of a number and
returns the result. If its argument is an array, the
`sinh' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
sqr
SYNOPSIS
Compute the square of a number
USAGE
y = sqr(x)
DESCRIPTION
The `sqr' function returns the square of an arithmetic type. If its
argument is a complex number (Complex_Type), then it returns
the square of the modulus. If the argument is an array, a new array
will be created whose elements are obtained from the original array
by using the `sqr' function.
NOTES
For real scalar numbers, using `x*x' instead of `sqr(x)'
will result in faster executing code. However, if `x' is an
array, then `sqr(x)' will execute faster.
SEE ALSO
abs, mul2
--------------------------------------------------------------
sqrt
SYNOPSIS
Compute the square root of a number
USAGE
y = sqrt (x)
DESCRIPTION
The `sqrt' function computes the square root of a number and
returns the result. If its argument is an array, the
`sqrt' function will be applied to each element and the result returned
as an array.
SEE ALSO
sqr, cos, atan, acosh, cosh
--------------------------------------------------------------
tan
SYNOPSIS
Compute the tangent of a number
USAGE
y = tan (x)
DESCRIPTION
The `tan' function computes the tangent of a number and
returns the result. If its argument is an array, the
`tan' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
tanh
SYNOPSIS
Compute the hyperbolic tangent of a number
USAGE
y = tanh (x)
DESCRIPTION
The `tanh' function computes the hyperbolic tangent of a number and
returns the result. If its argument is an array, the
`tanh' function will be applied to each element and the result returned
as an array.
SEE ALSO
cos, atan, acosh, cosh
--------------------------------------------------------------
_ispos
SYNOPSIS
Test if a number is greater than 0
USAGE
Char_Type _ispos(x)
DESCRIPTION
This function returns 1 if a number is greater than 0, and zero
otherwise. If the argument is an array, then the corresponding
array of boolean (Char_Type) values will be returned.
SEE ALSO
_isneg, _isnonneg
--------------------------------------------------------------
_isneg
SYNOPSIS
Test if a number is less than 0
USAGE
Char_Type _isneg(x)
DESCRIPTION
This function returns 1 if a number is less than 0, and zero
otherwise. If the argument is an array, then the corresponding
array of boolean (Char_Type) values will be returned.
SEE ALSO
_ispos, _isnonneg
--------------------------------------------------------------
_isnonneg
SYNOPSIS
Test if a number is greater than or equal to 0
USAGE
Char_Type _isnonneg(x)
DESCRIPTION
This function returns 1 if a number is greater or equal to 0, and zero
otherwise. If the argument is an array, then the corresponding
array of boolean (Char_Type) values will be returned.
SEE ALSO
_isneg, _isnonneg
--------------------------------------------------------------
errno
SYNOPSIS
Error code set by system functions
USAGE
Int_Type errno
DESCRIPTION
A system function can fail for a variety of reasons. For example, a
file operation may fail because lack of disk space, or the process
does not have permission to perform the operation. Such functions
will return -1 and set the variable `errno' to an error
code describing the reason for failure.
Particular values of `errno' may be specified by the following
symbolic constants (read-only variables) and the corresponding
`errno_string' value:
EPERM "Not owner"
ENOENT "No such file or directory"
ESRCH "No such process"
ENXIO "No such device or address"
ENOEXEC "Exec format error"
EBADF "Bad file number"
ECHILD "No children"
ENOMEM "Not enough core"
EACCES "Permission denied"
EFAULT "Bad address"
ENOTBLK "Block device required"
EBUSY "Mount device busy"
EEXIST "File exists"
EXDEV "Cross-device link"
ENODEV "No such device"
ENOTDIR "Not a directory"
EISDIR "Is a directory"
EINVAL "Invalid argument"
ENFILE "File table overflow"
EMFILE "Too many open files"
ENOTTY "Not a typewriter"
ETXTBSY "Text file busy"
EFBIG "File too large"
ENOSPC "No space left on device"
ESPIPE "Illegal seek"
EROFS "Read-only file system"
EMLINK "Too many links"
EPIPE "Broken pipe"
ELOOP "Too many levels of symbolic links"
ENAMETOOLONG "File name too long"
EXAMPLE
The `mkdir' function will attempt to create a directory. If
that directory already exists, the function will fail and set
`errno' to EEXIST.
define create_dir (dir)
{
if (0 == mkdir (dir)) return;
if (errno != EEXIST)
throw IOError, sprintf ("mkdir %s failed: %s",
dir, errno_string (errno));
}
SEE ALSO
errno_string, error, mkdir
--------------------------------------------------------------
errno_string
SYNOPSIS
Return a string describing an errno.
USAGE
String_Type errno_string ( [Int_Type err ])
DESCRIPTION
The `errno_string' function returns a string describing the
integer errno code `err'. If the `err' parameter is
omitted, the current value of `errno' will be used. See the
description for `errno' for more information.
EXAMPLE
The `errno_string' function may be used as follows:
define sizeof_file (file)
{
variable st = stat_file (file);
if (st == NULL)
throw IOError, sprintf ("%s: %s", file, errno_string (errno));
return st.st_size;
}
SEE ALSO
errno, stat_file
--------------------------------------------------------------
error
SYNOPSIS
Generate an error condition (deprecated)
USAGE
error (String_Type msg
DESCRIPTION
This function has been deprecated in favor of `throw'.
The `error' function generates a S-Lang `RunTimeError'
exception. It takes a single string parameter which is displayed on
the stderr output device.
EXAMPLE
define add_txt_extension (file)
{
if (typeof (file) != String_Type)
error ("add_extension: parameter must be a string");
file += ".txt";
return file;
}
SEE ALSO
verror, message
--------------------------------------------------------------
__get_exception_info
SYNOPSIS
Get information about the current exception
USAGE
Struct_Type __get_exception_info ()
DESCRIPTION
This function returns information about the currently active
exception in the form as a structure with the
following fields:
error The current exception, e.g., RunTimeError
descr A description of the exception
file Name of the file generating the exception
line Line number where the exception originated
function Function where the exception originated
object A user-defined object thrown by the exception
message A user-defined message
If no exception is active, NULL will be returned.
This same information may also be obtained via the optional argument
to the `try' statement:
variable e = NULL;
try (e)
{
do_something ();
}
finally
{
if (e != NULL)
vmessage ("An error occured: %s", e.message);
}
SEE ALSO
error
--------------------------------------------------------------
message
SYNOPSIS
Print a string onto the message device
USAGE
message (String_Type s
DESCRIPTION
The `message' function will print the string specified by
`s' onto the message device.
EXAMPLE
define print_current_time ()
{
message (time ());
}
NOTES
The message device will depend upon the application. For example,
the output message device for the jed editor corresponds to the
line at the bottom of the display window. The default message
device is the standard output device.
SEE ALSO
vmessage, sprintf, error
--------------------------------------------------------------
new_exception
SYNOPSIS
Create a new exception
USAGE
new_exception (String_Type name, Int_Type baseclass, String_Type descr)
DESCRIPTION
This function creates a new exception called `name' subclassed
upon `baseclass'. The description of the exception is
specified by `descr'.
EXAMPLE
new_exception ("MyError", RunTimeError, "My very own error");
try
{
if (something_is_wrong ())
throw MyError;
}
catch RunTimeError;
In this case, catching `RunTimeError' will also catch
`MyError' since it is a subclass of `RunTimeError'.
SEE ALSO
error, verror
--------------------------------------------------------------
usage
SYNOPSIS
Generate a usage error
USAGE
usage (String_Type msg)
DESCRIPTION
The `usage' function generates a `UsageError' exception and
displays `msg' to the message device.
EXAMPLE
Suppose that a function called `plot' plots an array of `x' and
`y' values. Then such a function could be written to issue a
usage message if the wrong number of arguments was passed:
define plot ()
{
variable x, y;
if (_NARGS != 2)
usage ("plot (x, y)");
(x, y) = ();
% Now do the hard part
.
.
}
SEE ALSO
error, message
--------------------------------------------------------------
verror
SYNOPSIS
Generate an error condition (deprecated)
USAGE
verror (String_Type fmt, ...)
DESCRIPTION
This function has been deprecated in favor or `throw'.
The `verror' function performs the same role as the `error'
function. The only difference is that instead of a single string
argument, `verror' takes a sprintf style argument list.
EXAMPLE
define open_file (file)
{
variable fp;
fp = fopen (file, "r");
if (fp == NULL) verror ("Unable to open %s", file);
return fp;
}
NOTES
In the current implementation, the `verror' function is not an
intrinsic function. Rather it is a predefined S-Lang function using
a combination of `sprintf' and `error'.
To generate a specific exception, a `throw' statement should be
used. In fact, a `throw' statement such as:
if (fp == NULL)
throw OpenError, "Unable to open $file"$;
is preferable to the use of `verror' in the above example.
SEE ALSO
error, Sprintf, vmessage
--------------------------------------------------------------
vmessage
SYNOPSIS
Print a formatted string onto the message device
USAGE
vmessage (String_Type fmt, ...)
DESCRIPTION
The `vmessage' function formats a sprintf style argument list
and displays the resulting string onto the message device.
NOTES
In the current implementation, the `vmessage' function is not an
intrinsic function. Rather it is a predefined S-Lang function using
a combination of `Sprintf' and `message'.
SEE ALSO
message, sprintf, Sprintf, verror
--------------------------------------------------------------
_auto_declare
SYNOPSIS
Set automatic variable declaration mode
USAGE
Integer_Type _auto_declare
DESCRIPTION
The `_auto_declare' variable may be used to have undefined
variable implicitly declared. If set to zero, any
variable must be declared with a `variable' declaration before it
can be used. If set to one, then any undeclared variable will be
declared as a `static' variable.
The `_auto_declare' variable is local to each compilation unit and
setting its value in one unit has no effect upon its value in other
units. The value of this variable has no effect upon the variables
in a function.
EXAMPLE
The following code will not compile if `X' not been
declared:
X = 1;
However,
_auto_declare = 1; % declare variables as static.
X = 1;
is equivalent to
static variable X = 1;
NOTES
This variable should be used sparingly and is intended primarily for
interactive applications where one types S-Lang commands at a
prompt.
--------------------------------------------------------------
__class_id
SYNOPSIS
Return the class-id of a specified type
USAGE
Int_Type __class_id (DataType_Type type)
DESCRIPTION
This function returns the internal class-id of a specified data type.
SEE ALSO
typeof, _typeof, __class_type, __datatype
--------------------------------------------------------------
__class_type
SYNOPSIS
Return the class-type of a specified type
USAGE
Int_Type __class_type (DataType_Type type))
DESCRIPTION
Internally S-Lang objects are classified according to four types:
scalar, vector, pointer, and memory managed types. For example, an
integer is implemented as a scalar, a complex number as a vector,
and a string is represented as a pointer. The `__class_type'
function returns an integer representing the class-type associated
with the specified data type. Specifically, it returns:
0 memory-managed
1 scalar
2 vector
3 pointer
SEE ALSO
typeof, _typeof, __class_id, __datatype
--------------------------------------------------------------
current_namespace
SYNOPSIS
Get the name of the current namespace
USAGE
String_Type current_namespace ()
DESCRIPTION
The `current_namespace' function returns the name of the
static namespace associated with the compilation unit. If there is
no such namespace associated with the compilation unit, then the
empty string `""' will be returned.
SEE ALSO
implements, use_namespace, import, evalfile
--------------------------------------------------------------
_eqs
SYNOPSIS
Test for equality of two objects
USAGE
Int_Type _eqs (a, b)
DESCRIPTION
This function tests its two arguments for equality and returns 1 if
they are equal or 0 otherwise. What it means to be equal depends
upon the data types of the objects being compared. If the types are
numeric, they are regarded as equal if their numerical values are
equal. If they are arrays, then they are equal if they have the
same shape with equal elements. If they are structures, then they
are equal if they contain identical fields, and the corresponding
values are equal.
EXAMPLE
_eqs (1, 1) ===> 1
_eqs (1, 1.0) ===> 1
_eqs ("a", 1) ===> 0
_eqs ([1,2], [1.0,2.0]) ===> 1
SEE ALSO
typeof, _eqs, __get_reference, __is_callable
NOTES
For testing sameness, use `__is_same'.
--------------------------------------------------------------
getenv
SYNOPSIS
Get the value of an environment variable
USAGE
String_Type getenv(String_Type var)
DESCRIPTION
The `getenv' function returns a string that represents the
value of an environment variable `var'. It will return
NULL if there is no environment variable whose name is given
by `var'.
EXAMPLE
if (NULL != getenv ("USE_COLOR"))
{
set_color ("normal", "white", "blue");
set_color ("status", "black", "gray");
USE_ANSI_COLORS = 1;
}
SEE ALSO
putenv, strlen, is_defined
--------------------------------------------------------------
__get_reference
SYNOPSIS
Get a reference to a global object
USAGE
Ref_Type __get_reference (String_Type nm)
DESCRIPTION
This function returns a reference to a global variable or function
whose name is specified by `nm'. If no such object exists, it
returns NULL, otherwise it returns a reference.
EXAMPLE
Consider the function:
define runhooks (hook)
{
variable f;
f = __get_reference (hook);
if (f != NULL)
@f ();
}
This function could be called from another S-Lang function to allow
customization of that function, e.g., if the function represents a
jed editor mode, the hook could be called to setup keybindings for
the mode.
SEE ALSO
is_defined, typeof, eval, autoload, __is_initialized, __uninitialize
--------------------------------------------------------------
implements
SYNOPSIS
Create a new static namespace
USAGE
implements (String_Type name)
DESCRIPTION
The `implements' function may be used to create a new static
namespace and have it associated with the current compilation unit.
If a namespace with the specified name already exists, a
`NamespaceError' exception will be thrown.
In addition to creating a new static namespace and associating it
with the compilation unit, the function will also create a new
private namespace. As a result, any symbols in the previous private
namespace will be no longer be accessable. For this reason, it is
recommended that this function should be used before any private
symbols have been created.
EXAMPLE
Suppose that some file `t.sl' contains:
implements ("My");
define message (x)
{
Global->message ("My's message: $x"$);
}
message ("hello");
will produce `"My's message: hello"'. This `message'
function may be accessed from outside the namespace via:
My->message ("hi");
NOTES
Since `message' is an intrinsic function, it is public and may
not be redefined in the public namespace.
The `implements' function should rarely be used. It is
preferable to allow a static namespace to be associated with a
compilation unit using, e.g., `evalfile'.
SEE ALSO
use_namespace, current_namespace, import
--------------------------------------------------------------
__is_callable
SYNOPSIS
Determine whether or not an object is callable
USAGE
Int_Type __is_callable (obj)
DESCRIPTION
This function may be used to determine if an object is callable by
dereferencing the object. It returns 1 if the argument is callable,
or zero otherwise.
EXAMPLE
__is_callable (7) ==> 0
__is_callable (&sin) ==> 1
a = [&sin];
__is_callable (a[0]) ==> 1
__is_callable (&a[0]) ==> 0
SEE ALSO
__is_numeric, is_defined
--------------------------------------------------------------
__is_numeric
SYNOPSIS
Determine whether or not an object is a numeric type
USAGE
Int_Type __is_numeric (obj)
DESCRIPTION
This function may be used to determine if an object represents a
numeric type. It returns 0 if the argument is non-numeric, 1 if it
is an integer, 2 if a floating point number, and 3 if it is complex.
If the argument is an array, then the array type will be used for
the test.
EXAMPLE
__is_numeric ("foo"); ==> 0
__is_numeric ("0"); ==> 0
__is_numeric (0); ==> 1
__is_numeric (PI); ==> 2
__is_numeric (2j); ==> 3
__is_numeric ([1,2]); ==> 1
__is_numeric ({1,2}); ==> 0
SEE ALSO
typeof, __is_datatype_numeric
--------------------------------------------------------------
__is_datatype_numeric
SYNOPSIS
Determine whether or not a type is a numeric type
USAGE
Int_Type __is_datatype_numeric (DataType_Type type)
DESCRIPTION
This function may be used to determine if the specified datatype
represents a numeric type. It returns 0 if the datatype does not
represents a numeric type; otherwise it returns 1 for an
integer type, 2 for a floating point type, and 3 for a complex type.
SEE ALSO
typeof, __is_numeric, __is_callable
--------------------------------------------------------------
__is_same
SYNOPSIS
Test for sameness of two objects
USAGE
Int_Type __is_same (a, b)
DESCRIPTION
This function tests its two arguments for sameness and returns 1
if they are the same, or 0 otherwise. To be the same, the data type of
the arguments must match and the values of the objects must
reference the same underlying object.
EXAMPLE
__is_same (1, 1) ===> 1
__is_same (1, 1.0) ===> 0
__is_same ("a", 1) ===> 0
__is_same ([1,2], [1,2]) ===> 0
SEE ALSO
typeof, _eqs, __get_reference, __is_callable
NOTES
For testing equality, use `_eqs'.
--------------------------------------------------------------
putenv
SYNOPSIS
Add or change an environment variable
USAGE
putenv (String_Type s)
DESCRIPTION
This functions adds string `s' to the environment. Typically,
`s' should of the form `"name=value"'. The function
throws an `OSError' upon failure.
NOTES
This function may not be available on all systems.
SEE ALSO
getenv, sprintf
--------------------------------------------------------------
_slang_install_prefix
SYNOPSIS
S-Lang's installation prefix
USAGE
String_Type _slang_install_prefix
DESCRIPTION
The value of this variable is set at the S-Lang library's
compilation time. On Unix systems, the value corresponds to the
value of the `prefix' variable in the Makefile. For normal
installations, the library itself will be located in the `lib'
subdirectory of the `prefix' directory.
NOTES
The value of this variable may or may not have anything to do with
where the slang library is located. As such, it should be regarded
as a hint. A standard installation will have the `slsh'
library files located in the `share/slsh' subdirectory of the
installation prefix.
SEE ALSO
_slang_doc_dir
--------------------------------------------------------------
_slang_utf8_ok
SYNOPSIS
Test if the interpreter running in UTF-8 mode
USAGE
Int_Type _slang_utf8_ok
DESCRIPTION
If the value of this variable is non-zero, then the interpreter is
running in UTF-8 mode. In this mode, characters in strings are
interpreted as variable length byte sequences according to the
semantics of the UTF-8 encoding.
NOTES
When running in UTF-8 mode, one must be careful not to confuse a
character with a byte. For example, in this mode the `strlen'
function returns the number of characters in a string which may be
different than the number of bytes. The latter information may be
obtained by the `strbytelen' function.
SEE ALSO
strbytelen, strlen, strcharlen
--------------------------------------------------------------
__uninitialize
SYNOPSIS
Uninitialize a variable
USAGE
__uninitialize (Ref_Type x)
DESCRIPTION
The `__uninitialize' function may be used to uninitialize the
variable referenced by the parameter `x'.
EXAMPLE
The following two lines are equivalent:
() = __tmp(z);
__uninitialize (&z);
SEE ALSO
__tmp, __is_initialized
--------------------------------------------------------------
use_namespace
SYNOPSIS
Change to another namespace
USAGE
use_namespace (String_Type name)
DESCRIPTION
The `use_namespace' function changes the current static namespace to
the one specified by the parameter. If the specified namespace
does not exist, a `NamespaceError' exception will be generated.
SEE ALSO
implements, current_namespace, import
--------------------------------------------------------------
path_basename
SYNOPSIS
Get the basename part of a filename
USAGE
String_Type path_basename (String_Type filename)
DESCRIPTION
The `path_basename' function returns the basename associated
with the `filename' parameter. The basename is the non-directory
part of the filename, e.g., on unix `c' is the basename of
`/a/b/c'.
SEE ALSO
path_dirname, path_extname, path_concat, path_is_absolute
--------------------------------------------------------------
path_basename_sans_extname
SYNOPSIS
Get the basename part of a filename but without the extension
USAGE
String_Type path_basename_sans_extname (String_Type path)
DESCRIPTION
The `path_basename_sans_extname' function returns the basename
associated with the `filename' parameter, omitting the
extension if present. The basename is the non-directory part of
the filename, e.g., on unix `c' is the basename of
`/a/b/c'.
SEE ALSO
path_dirname, path_basename, path_extname, path_concat, path_is_absolute
--------------------------------------------------------------
path_concat
SYNOPSIS
Combine elements of a filename
USAGE
String_Type path_concat (String_Type dir, String_Type basename)
DESCRIPTION
The `path_concat' function combines the arguments `dir' and
`basename' to produce a filename. For example, on Unix if
`dir' is `x/y' and `basename' is `z', then the
function will return `x/y/z'.
SEE ALSO
path_dirname, path_basename, path_extname, path_is_absolute
--------------------------------------------------------------
path_dirname
SYNOPSIS
Get the directory name part of a filename
USAGE
String_Type path_dirname (String_Type filename)
DESCRIPTION
The `path_dirname' function returns the directory name
associated with a specified filename.
NOTES
On systems that include a drive specifier as part of the filename,
the value returned by this function will also include the drive
specifier.
SEE ALSO
path_basename, path_extname, path_concat, path_is_absolute
--------------------------------------------------------------
path_extname
SYNOPSIS
Return the extension part of a filename
USAGE
String_Type path_extname (String_Type filename)
DESCRIPTION
The `path_extname' function returns the extension portion of the
specified filename. If an extension is present, this function will
also include the dot as part of the extension, e.g., if `filename'
is `"file.c"', then this function will return `".c"'. If no
extension is present, the function returns an empty string `""'.
NOTES
Under VMS, the file version number is not returned as part of the
extension.
SEE ALSO
path_sans_extname, path_dirname, path_basename, path_concat, path_is_absolute
--------------------------------------------------------------
path_get_delimiter
SYNOPSIS
Get the value of a search-path delimiter
USAGE
Char_Type path_get_delimiter ()
DESCRIPTION
This function returns the value of the character used to delimit
fields of a search-path.
SEE ALSO
set_slang_load_path, get_slang_load_path
--------------------------------------------------------------
path_is_absolute
SYNOPSIS
Determine whether or not a filename is absolute
USAGE
Int_Type path_is_absolute (String_Type filename)
DESCRIPTION
The `path_is_absolute' function will return non-zero is
`filename' refers to an absolute filename, otherwise it returns zero.
SEE ALSO
path_dirname, path_basename, path_extname, path_concat
--------------------------------------------------------------
path_sans_extname
SYNOPSIS
Strip the extension from a filename
USAGE
String_Type path_sans_extname (String_Type filename)
DESCRIPTION
The `path_sans_extname' function removes the file name extension
(including the dot) from the filename and returns the result.
SEE ALSO
path_basename_sans_extname, path_extname, path_basename, path_dirname, path_concat
--------------------------------------------------------------
close
SYNOPSIS
Close an open file descriptor
USAGE
Int_Type close (FD_Type fd)
DESCRIPTION
The `close' function is used to close and open file descriptor
created by the `open' function. Upon success 0 is returned,
otherwise the function returns -1 and sets `errno' accordingly.
SEE ALSO
open, fclose, read, write
--------------------------------------------------------------
dup_fd
SYNOPSIS
Duplicate a file descriptor
USAGE
FD_Type dup_fd (FD_Type fd)
DESCRIPTION
The `dup_fd' function duplicates a specified file descriptor and
returns the duplicate. If the function fails, NULL will be
returned and `errno' set accordingly.
NOTES
This function is essentially a wrapper around the POSIX `dup'
function.
SEE ALSO
open, close
--------------------------------------------------------------
fileno
SYNOPSIS
Convert a stdio File_Type object to a FD_Type descriptor
USAGE
FD_Type fileno (File_Type fp)
DESCRIPTION
The `fileno' function returns the FD_Type descriptor
associated with the stdio File_Type file pointer. Upon failure,
NULL is returned.
SEE ALSO
fopen, open, fclose, close, dup_fd
--------------------------------------------------------------
isatty
SYNOPSIS
Determine if an open file descriptor refers to a terminal
USAGE
Int_Type isatty (FD_Type or File_Type fd)
DESCRIPTION
This function returns 1 if the file descriptor `fd' refers to a
terminal; otherwise it returns 0. The object `fd' may either
be a File_Type stdio descriptor or a lower-level FD_Type
object.
SEE ALSO
fopen, fclose, fileno
--------------------------------------------------------------
lseek
SYNOPSIS
Reposition a file descriptor's file pointer
USAGE
Long_Type lseek (FD_Type fd, LLong_Type ofs, int mode)
The `lseek' function repositions the file pointer associated
with the open file descriptor `fd' to the offset `ofs'
according to the mode parameter. Specifically, `mode' must be
one of the values:
SEEK_SET Set the offset to ofs from the beginning of the file
SEEK_CUR Add ofs to the current offset
SEEK_END Add ofs to the current file size
Upon error, `lseek' returns -1 and sets `errno'. If
successful, it returns the new filepointer offset.
NOTES
Not all file descriptors are capable of supporting the seek
operation, e.g., a descriptor associated with a pipe.
By using SEEK_END with a positive value of the `ofs'
parameter, it is possible to position the file pointer beyond the
current size of the file.
SEE ALSO
fseek, ftell, open, close
--------------------------------------------------------------
open
SYNOPSIS
Open a file
USAGE
FD_Type open (String_Type filename, Int_Type flags [,Int_Type mode])
DESCRIPTION
The `open' function attempts to open a file specified by the
`filename' parameter according to the `flags' parameter,
which must be one of the following values:
O_RDONLY (read-only)
O_WRONLY (write-only)
O_RDWR (read/write)
In addition, `flags' may also be bitwise-or'd with any of the
following:
O_BINARY (open the file in binary mode)
O_TEXT (open the file in text mode)
O_CREAT (create the file if it does not exist)
O_EXCL (fail if the file already exists)
O_NOCTTY (do not make the device the controlling terminal)
O_TRUNC (truncate the file if it exists)
O_APPEND (open the file in append mode)
O_NONBLOCK (open the file in non-blocking mode)
Some of these flags make sense only when combined with other flags.
For example, if O_EXCL is used, then O_CREAT must also be
specified, otherwise unpredictable behavior may result.
If O_CREAT is used for the `flags' parameter then the
`mode' parameter must be present. `mode' specifies the
permissions to use if a new file is created. The actual file
permissions will be affected by the process's `umask' via
`mode&~umask'. The `mode' parameter's value is
constructed via bitwise-or of the following values:
S_IRWXU (Owner has read/write/execute permission)
S_IRUSR (Owner has read permission)
S_IWUSR (Owner has write permission)
S_IXUSR (Owner has execute permission)
S_IRWXG (Group has read/write/execute permission)
S_IRGRP (Group has read permission)
S_IWGRP (Group has write permission)
S_IXGRP (Group has execute permission)
S_IRWXO (Others have read/write/execute permission)
S_IROTH (Others have read permission)
S_IWOTH (Others have write permission)
S_IXOTH (Others have execute permission)
Upon success `open' returns a file descriptor object
(FD_Type), otherwise NULL is returned and `errno'
is set.
NOTES
If you are not familiar with the `open' system call, then it
is recommended that you use `fopen' instead and use the higher
level stdio interface.
SEE ALSO
fopen, close, read, write, stat_file
--------------------------------------------------------------
read
SYNOPSIS
Read from an open file descriptor
USAGE
UInt_Type read (FD_Type fd, Ref_Type buf, UInt_Type num)
DESCRIPTION
The `read' function attempts to read at most `num' bytes
into the variable indicated by `buf' from the open file
descriptor `fd'. It returns the number of bytes read, or -1
upon failure and sets `errno'. The number of bytes
read may be less than `num', and will be zero if an attempt is
made to read past the end of the file.
NOTES
`read' is a low-level function and may return -1 for a variety
of reasons. For example, if non-blocking I/O has been specified for
the open file descriptor and no data is available for reading then
the function will return -1 and set `errno' to EAGAIN.
SEE ALSO
fread, open, close, write
--------------------------------------------------------------
write
SYNOPSIS
Write to an open file descriptor
USAGE
UInt_Type write (FD_Type fd, BString_Type buf)
DESCRIPTION
The `write' function attempts to write the bytes specified by
the `buf' parameter to the open file descriptor `fd'. It
returns the number of bytes successfully written, or -1 and sets
`errno' upon failure. The number of bytes written may be less
than `length(buf)'.
SEE ALSO
read, fwrite, open, close
--------------------------------------------------------------
getegid
SYNOPSIS
Get the effective group id of the current process
USAGE
Int_Type getegid ()
DESCRIPTION
The `getegid' function returns the effective group ID of the
current process.
NOTES
This function is not supported by all systems.
SEE ALSO
getgid, geteuid, setgid
--------------------------------------------------------------
geteuid
SYNOPSIS
Get the effective user-id of the current process
USAGE
Int_Type geteuid ()
DESCRIPTION
The `geteuid' function returns the effective user-id of the
current process.
NOTES
This function is not supported by all systems.
SEE ALSO
getuid, setuid, setgid
--------------------------------------------------------------
getgid
SYNOPSIS
Get the group id of the current process
USAGE
Integer_Type getgid ()
DESCRIPTION
The `getgid' function returns the real group id of the current
process.
NOTES
This function is not supported by all systems.
SEE ALSO
getpid, getppid
--------------------------------------------------------------
getpid
SYNOPSIS
Get the current process id
USAGE
Integer_Type getpid ()
DESCRIPTION
The `getpid' function returns the current process identification
number.
SEE ALSO
getppid, getgid
--------------------------------------------------------------
getppid
SYNOPSIS
Get the parent process id
USAGE
Integer_Type getppid ()
DESCRIPTION
The `getpid' function returns the process identification
number of the parent process.
NOTES
This function is not supported by all systems.
SEE ALSO
getpid, getgid
--------------------------------------------------------------
getuid
SYNOPSIS
Get the user-id of the current process
USAGE
Int_Type getuid ()
DESCRIPTION
The `getuid' function returns the user-id of the current
process.
NOTES
This function is not supported by all systems.
SEE ALSO
getuid, getegid
--------------------------------------------------------------
kill
SYNOPSIS
Send a signal to a process
USAGE
Integer_Type kill (Integer_Type pid, Integer_Type sig)
DESCRIPTION
This function may be used to send a signal given by the integer `sig'
to the process specified by `pid'. The function returns zero upon
success or `-1' upon failure setting `errno' accordingly.
EXAMPLE
The `kill' function may be used to determine whether or not
a specific process exists:
define process_exists (pid)
{
if (-1 == kill (pid, 0))
return 0; % Process does not exist
return 1;
}
NOTES
This function is not supported by all systems.
SEE ALSO
getpid
--------------------------------------------------------------
mkfifo
SYNOPSIS
Create a named pipe
USAGE
Int_Type mkfifo (String_Type name, Int_Type mode)
DESCRIPTION
The `mkfifo' attempts to create a named pipe with the specified
name and mode (modified by the process's umask). The function
returns 0 upon success, or -1 and sets `errno' upon failure.
NOTES
Not all systems support the `mkfifo' function and even on
systems that do implement the `mkfifo' system call, the
underlying file system may not support the concept of a named pipe,
e.g, an NFS filesystem.
SEE ALSO
stat_file
--------------------------------------------------------------
setgid
SYNOPSIS
Set the group-id of the current process
USAGE
Int_Type setgid (Int_Type gid)
DESCRIPTION
The `setgid' function sets the effective group-id of the current
process. It returns zero upon success, or -1 upon error and sets
`errno' appropriately.
NOTES
This function is not supported by all systems.
SEE ALSO
getgid, setuid
--------------------------------------------------------------
setpgid
SYNOPSIS
Set the process group-id
USAGE
Int_Type setpgid (Int_Type pid, Int_Type gid)
DESCRIPTION
The `setpgid' function sets the group-id `gid' of the
process whose process-id is `pid'. If `pid' is 0, then the
current process-id will be used. If `pgid' is 0, then the pid
of the affected process will be used.
If successful 0 will be returned, otherwise the function will
return -1 and set `errno' accordingly.
NOTES
This function is not supported by all systems.
SEE ALSO
setgid, setuid
--------------------------------------------------------------
setuid
SYNOPSIS
Set the user-id of the current process
USAGE
Int_Type setuid (Int_Type id)
DESCRIPTION
The `setuid' function sets the effective user-id of the current
process. It returns zero upon success, or -1 upon error and sets
`errno' appropriately.
NOTES
This function is not supported by all systems.
SEE ALSO
setgid, setpgid, getuid, geteuid
--------------------------------------------------------------
sleep
SYNOPSIS
Pause for a specified number of seconds
USAGE
sleep (Double_Type n)
DESCRIPTION
The `sleep' function delays the current process for the
specified number of seconds. If it is interrupted by a signal, it
will return prematurely.
NOTES
Not all system support sleeping for a fractional part of a second.
--------------------------------------------------------------
system
SYNOPSIS
Execute a shell command
USAGE
Integer_Type system (String_Type cmd)
DESCRIPTION
The `system' function may be used to execute the string
expression `cmd' in an inferior shell. This function is an
interface to the C `system' function which returns an
implementation-defined result. On Linux, it returns 127 if the
inferior shell could not be invoked, -1 if there was some other
error, otherwise it returns the return code for `cmd'.
EXAMPLE
define dir ()
{
() = system ("DIR");
}
displays a directory listing of the current directory under MSDOS or
VMS.
SEE ALSO
popen, listdir
--------------------------------------------------------------
umask
SYNOPSIS
Set the file creation mask
USAGE
Int_Type umask (Int_Type m)
DESCRIPTION
The `umask' function sets the file creation mask to the value of
`m' and returns the previous mask.
SEE ALSO
stat_file
--------------------------------------------------------------
uname
SYNOPSIS
Get the system name
USAGE
Struct_Type uname ()
DESCRIPTION
The `uname' function returns a structure containing information
about the operating system. The structure contains the following
fields:
sysname (Name of the operating system)
nodename (Name of the node within the network)
release (Release level of the OS)
version (Current version of the release)
machine (Name of the hardware)
NOTES
Not all systems support this function.
SEE ALSO
getenv
--------------------------------------------------------------
qualifier
SYNOPSIS
Get the value of a qualifier
USAGE
value = qualifier (String_Type name [,default_value])
DESCRIPTION
This function may be used to get the value of a qualifer. If the
specified qualifier does not exist, `NULL' will be returned,
unless a default value has been provided.
EXAMPLE
define echo (text)
{
variable fp = qualifier ("out", stdout);
() = fputs (text, fp);
}
echo ("hello"); % writes hello to stdout
echo ("hello"; out=stderr); % writes hello to stderr
NOTES
Since `NULL' is a valid value for a qualifier, this function is
unable to distinguish between a non-existent qualifier and one whose
value is `NULL'. If such a distinction is important, the
`qualifier_exists' function can be used. For example,
define echo (text)
{
variable fp = stdout;
if (qualifier_exists ("use_stderr"))
fp = stderr;
() = fputs (text, fp);
}
echo ("hello"; use_stderr); % writes hello to stderr
In this case, no value was provided for the `use_stderr'
qualifier: it exists but has a value of `NULL'.
SEE ALSO
qualifier_exists, __qualifiers
--------------------------------------------------------------
__qualifiers
SYNOPSIS
Get the active set of qualifiers
USAGE
Struct_Type __qualifiers ()
DESCRIPTION
This function returns the set of qualifiers associated with the
current execution context. If qualifiers are active, then the result
is a structure representing the names of the qualifiers and their
corresponding values. Otherwise `NULL' will be returned.
One of the main uses of this function is to pass the current set of
qualifiers to another another function. For example, consider a
plotting application with a function called called `lineto' that
sets the pen-color before drawing the line to the specified point:
define lineto (x, y)
{
% The color may be specified by a qualifier, defaulting to black
variable color = qualifier ("color", "black");
set_pen_color (color);
.
.
}
The `lineto' function permits the color to be specified by a
qualifier. Now consider a function that make use of lineto to draw a
line segment between two points:
define line_segment (x0, y0, x1, y1)
{
moveto (x0, y0);
lineto (x1, y1 ; color=qualifier("color", "black"));
}
line_segment (1,1, 10,10; color="blue");
Note that in this implementation of `line_segment', the
`color' qualifier was explicitely passed to the `lineto'
function. However, this technique does not scale well. For example, the
`lineto' function might also take a qualifer that specifies the
line-style, to be used as
line_segment (1,1, 10,10; color="blue", linestyle="solid");
But the above implementation of `line_segment' does not pass the
`linestyle' qualifier. In such a case, it is preferable to pass
all the qualifiers, e.g.,
define line_segment (x0, y0, x1, y1)
{
moveto (x0, y0);
lineto (x1, y1 ;; __qualifiers());
}
Note the use of the double-semi colon in the `lineto'
statement. This tells the parser that the qualifiers are specified
by a structure-valued argument and not a set of name-value pairs.
SEE ALSO
qualifier, qualifier_exists
--------------------------------------------------------------
qualifier_exists
SYNOPSIS
Check for the existence of a qualifier
USAGE
Int_Type qualifier_exists (String_Type name)
DESCRIPTION
This function will return 1 if a qualifier of the specified name
exists, or 0 otherwise.
SEE ALSO
qualifier, __qualifiers
--------------------------------------------------------------
alarm
SYNOPSIS
Schedule an alarm signal
USAGE
alarm (UInt_Type secs [, Ref_Type secs_remaining])
DESCRIPTION
The `alarm' function schedules the delivery of a SIGALRM
signal in `secs' seconds. Any previously scheduled alarm will
be canceled. If `secs' is zero, then no new alarm will be
scheduled. If the second argument is present, then it must be a
reference to a variable whose value will be set upon return to the
number of seconds remaining for a previously scheduled alarm to take
place.
EXAMPLE
This example shows demonstrates how the `alarm' function may be
used to read from a file within a specified amount of time:
define sigalrm_handler (sig)
{
throw ReadError, "Read timed out";
}
define read_or_timeout (secs)
{
variable line, e;
variable fp = fopen ("/dev/tty", "r");
signal (SIGALRM, &sigalrm_handler);
alarm (secs);
try (e)
{
() = fputs ("Enter some text> ", stdout); () = fflush (stdout);
if (-1 == fgets (&line, fp))
line = NULL;
}
catch IOError: { message (e.message); line = NULL; }
return line;
}
NOTES
Some operating systems may implement the `sleep' function using
`alarm'. As a result, it is not a good idea to mix calls to
`alarm' and `sleep'.
The default action for SIGALRM is to terminate the process.
Hence, if `alarm' is called it is wise to establish a signal
handler for `SIGALRM'.
SEE ALSO
signal, sleep
--------------------------------------------------------------
signal
SYNOPSIS
Establish a signal handler
USAGE
signal (Int_Type sig, Ref_Type func [,Ref_Type old_func])
DESCRIPTION
The `signal' function assigns the signal handler represented by
`func' to the signal `sig'. Here `func' is usually
reference to a function that takes an integer argument (the signal)
and returns nothing, e.g.,
define signal_handler (sig)
{
return;
}
Alternatively, `func' may be given by one of the symbolic
constants SIG_IGN or SIG_DFL to indicate that the
signal is to be ignored or given its default action, respectively.
The first parameter, `sig', specifies the signal to be handled.
The actual supported values vary with the OS. Common values on Unix
include `SIGHUP', `SIGINT', and `SIGTERM'.
If a third argument is present, then it must be a reference to a
variable whose value will be set to the value of the previously
installed handler.
EXAMPLE
This example establishes a handler for `SIGTSTP'.
static define sig_suspend (); % forward declaration
static define sig_suspend (sig)
{
message ("SIGTSTP received-- stopping");
signal (sig, SIG_DFL);
() = kill (getpid(), SIGSTOP);
message ("Resuming");
signal (sig, &sig_suspend);
}
signal (SIGTSTP, &sig_suspend);
NOTES
Currently the signal interface is supported only on systems that
implement signals according to the POSIX standard.
Once a signal has been received, it will remain blocked until after
the signal handler has completed. This is the reason SIGSTOP
was used in the above signal handler instead of SIGTSTP.
SEE ALSO
alarm, sigsuspend, sigprocmask
--------------------------------------------------------------
sigprocmask
SYNOPSIS
Change the list of currently blocked signals
USAGE
sigprocmask (Int_Type how, Array_Type mask [,Ref_Type old_mask])
DESCRIPTION
The `sigprocmask' function may be used to change the list of
signals that are currently blocked. The first parameter indicates
how this is accomplished. Specifically, `how' must be one of
the following values: SIG_BLOCK, SIG_UNBLOCK, or
SIG_SETMASK.
If `how' is SIG_BLOCK, then the set of blocked signals
will be the union the current set with the values specified in the
`mask' argument.
If `how' is SIG_UNBLOCK, then the signals specified by
the `mask' parameter will be removed from the currently blocked
set.
If `how' is SIG_SETMASK, then the set of blocked signals
will be set to those given by the `mask'.
If a third argument is present, then it must be a reference to a
variable whose value will be set to the previous signal mask.
SEE ALSO
signal, sigsuspend, alarm
--------------------------------------------------------------
sigsuspend
SYNOPSIS
Suspend the process until a signal is delivered
USAGE
sigsuspend ([Array_Type signal_mask])
DESCRIPTION
The
sigsuspend
function suspends the current process
until a signal is received. An optional array argument may be
passed to the function to specify a list of signals that should be
temporarily blocked while waiting for a signal.
EXAMPLE
The following example pauses the current process for 10 seconds
while blocking the SIGHUP and SIGINT signals.
static variable Tripped;
define sigalrm_handler (sig)
{
Tripped = 1;
}
signal (SIGALRM, &sigalrm_handler);
Tripped = 0;
alarm (10);
while (Tripped == 0) sigsuspend ([SIGHUP, SIGINT]);
Note that in this example the call to `sigsuspend' was wrapped in
a while-loop. This was necessary because there is no guarantee that
another signal would not cause `sigsuspend' to return.
SEE ALSO
signal, alarm, sigprocmask
--------------------------------------------------------------
dup
SYNOPSIS
Duplicate the value at the top of the stack
USAGE
dup ()
DESCRIPTION
This function returns an exact duplicate of the object on top of the
stack. For some objects such as arrays or structures, it creates a
new reference to the object. However, for simple scalar S-Lang types such
as strings, integers, and doubles, it creates a new copy of the
object.
SEE ALSO
pop, typeof
--------------------------------------------------------------
exch
SYNOPSIS
Exchange two items on the stack
USAGE
exch ()
DESCRIPTION
The `exch' swaps the two top items on the stack.
SEE ALSO
pop, _stk_reverse, _stk_roll
--------------------------------------------------------------
pop
SYNOPSIS
Discard an item from the stack
USAGE
pop ()
DESCRIPTION
The `pop' function removes the top item from the stack.
SEE ALSO
_pop_n, __pop_args
--------------------------------------------------------------
__pop_args
SYNOPSIS
Remove n function arguments from the stack
USAGE
args = __pop_args(Integer_Type n)
DESCRIPTION
This function, together with the companion function
`__push_args', is useful for creating a function that takes a
variable number of arguments, as well as passing the arguments of
one function to another function.
`__pop_args' removes the specified number of values from the
stack and returns them as an array of structures of the corresponding
length. Each structure in the array consists of a single
field called `value', which represents the value of the
argument.
EXAMPLE
Consider the following function. It prints all its arguments to
`stdout' separated by spaces:
define print_args ()
{
variable i;
variable args = __pop_args (_NARGS);
for (i = 0; i < _NARGS; i++)
{
() = fputs (string (args[i].value), stdout);
() = fputs (" ", stdout);
}
() = fputs ("\n", stdout);
() = fflush (stdout);
}
Now consider the problem of defining a function called `ones'
that returns a multi-dimensional array with all the elements set to
1. For example, `ones(10)' should return a 1-d array of 10
ones, whereas `ones(10,20)' should return a 10x20 array.
define ones ()
{
!if (_NARGS) return 1;
variable a;
a = __pop_args (_NARGS);
return @Array_Type (Integer_Type, [__push_args (a)]) + 1;
}
Here, `__push_args' was used to push the arguments passed to
the `ones' function onto the stack to be used when dereferencing
Array_Type.
NOTES
This function has been superseded by the `__pop_list' function,
which returns the objects as a list instead of an array of structures.
SEE ALSO
__push_args, __pop_list, __push_list, typeof, _pop_n
--------------------------------------------------------------
__pop_list
SYNOPSIS
Convert items on the stack to a List_Type
USAGE
List_Type = __pop_list (Int_Type n)
DESCRIPTION
This function removes a specified number of items from the stack and
converts returns them in the form of a list.
EXAMPLE
define print_args ()
{
variable list = __pop_list (_NARGS);
variable i;
_for i (0, length(length)-1, 1)
{
vmessage ("arg[%d]: %S", list[i]);
}
}
NOTES
SEE ALSO
__push_list
--------------------------------------------------------------
_pop_n
SYNOPSIS
Remove objects from the stack
USAGE
_pop_n (Integer_Type n);
DESCRIPTION
The `_pop_n' function removes the specified number of objects
from the top of the stack.
SEE ALSO
_stkdepth, pop
--------------------------------------------------------------
_print_stack
SYNOPSIS
Print the values on the stack.
USAGE
_print_stack ()
DESCRIPTION
This function dumps out what is currently on the S-Lang stack. It does not
alter the stack and it is usually used for debugging purposes.
SEE ALSO
_stkdepth, string, message
--------------------------------------------------------------
__push_args
SYNOPSIS
Move n function arguments onto the stack
USAGE
__push_args (Struct_Type args);
DESCRIPTION
This function together with the companion function `__pop_args'
is useful for the creation of functions that take a variable number
of arguments. See the description of `__pop_args' for more
information.
NOTES
This function has been superseded by the `__push_list' function.
SEE ALSO
__pop_args, __push_list, __pop_list, typeof, _pop_n
--------------------------------------------------------------
__push_list
SYNOPSIS
Push the elements of a list to the stack
USAGE
__push_list (List_Type list)
DESCRIPTION
This function pushes the elements of a list to the stack.
EXAMPLE
private variable list_to_array (list)
{
return [__push_list (list)];
}
SEE ALSO
__pop_list
--------------------------------------------------------------
_stkdepth
USAGE
Get the number of objects currently on the stack
SYNOPSIS
Integer_Type _stkdepth ()
DESCRIPTION
The `_stkdepth' function returns number of items on the stack.
SEE ALSO
_print_stack, _stk_reverse, _stk_roll
--------------------------------------------------------------
_stk_reverse
SYNOPSIS
Reverse the order of the objects on the stack
USAGE
_stk_reverse (Integer_Type n)
DESCRIPTION
The `_stk_reverse' function reverses the order of the top
`n' items on the stack.
SEE ALSO
_stkdepth, _stk_roll
--------------------------------------------------------------
_stk_roll
SYNOPSIS
Roll items on the stack
USAGE
_stk_roll (Integer_Type n)
DESCRIPTION
This function may be used to alter the arrangement of objects on the
stack. Specifically, if the integer `n' is positive, the top
`n' items on the stack are rotated up. If
`n' is negative, the top `abs(n)' items on the stack are
rotated down.
EXAMPLE
If the stack looks like:
item-0
item-1
item-2
item-3
where `item-0' is at the top of the stack, then
`_stk_roll(-3)' will change the stack to:
item-2
item-0
item-1
item-3
NOTES
This function only has an effect if `abs(n) > 1'.
SEE ALSO
_stkdepth, _stk_reverse, _pop_n, _print_stack
--------------------------------------------------------------
clearerr
SYNOPSIS
Clear the error of a file stream
USAGE
clearerr (File_Type fp
DESCRIPTION
The `clearerr' function clears the error and end-of-file flags
associated with the open file stream `fp'.
SEE ALSO
ferror, feof, fopen
--------------------------------------------------------------
fclose
SYNOPSIS
Close a file
USAGE
Integer_Type fclose (File_Type fp)
DESCRIPTION
The `fclose' function may be used to close an open file pointer
`fp'. Upon success it returns zero, and upon failure it sets
`errno' and returns `-1'. Failure usually indicates a that
the file system is full or that `fp' does not refer to an open file.
NOTES
Many C programmers call `fclose' without checking the return
value. The S-Lang language requires the programmer to explicitly
handle any value returned by a function. The simplest way to
handle the return value from `fclose' is to call it via:
() = fclose (fp);
SEE ALSO
fopen, fgets, fflush, pclose, errno
--------------------------------------------------------------
fdopen
SYNOPSIS
Convert a FD_Type file descriptor to a stdio File_Type object
USAGE
File_Type fdopen (FD_Type, String_Type mode)
DESCRIPTION
The `fdopen' function creates and returns a stdio
File_Type object from the open FD_Type
descriptor `fd'. The `mode' parameter corresponds to the
`mode' parameter of the `fopen' function and must be
consistent with the mode of the descriptor `fd'. The function
returns NULL upon failure and sets `errno'.
NOTES
The `fclose' function does not close the File_Type object
returned from this function. The underlying file object must be
closed by the `close' function.
SEE ALSO
fileno, fopen, open, close, fclose
--------------------------------------------------------------
feof
SYNOPSIS
Get the end-of-file status
USAGE
Integer_Type feof (File_Type fp)
DESCRIPTION
This function may be used to determine the state of the end-of-file
indicator of the open file descriptor `fp'. It returns zero
if the indicator is not set, or non-zero if it is. The end-of-file
indicator may be cleared by the `clearerr' function.
SEE ALSO
ferror, clearerr, fopen
--------------------------------------------------------------
ferror
SYNOPSIS
Determine the error status of an open file descriptor
USAGE
Integer_Type ferror (File_Type fp)
DESCRIPTION
This function may be used to determine the state of the error
indicator of the open file descriptor `fp'. It returns zero
if the indicator is not set, or non-zero if it is. The error
indicator may be cleared by the `clearerr' function.
SEE ALSO
feof, clearerr, fopen
--------------------------------------------------------------
fflush
SYNOPSIS
Flush an output stream
USAGE
Integer_Type fflush (File_Type fp)
DESCRIPTION
The `fflush' function may be used to update the stdio _output_
stream specified by `fp'. It returns 0 upon success, or
-1 upon failure and sets `errno' accordingly. In
particular, this function will fail if `fp' does not represent
an open output stream, or if `fp' is associated with a disk file and
there is insufficient disk space.
EXAMPLE
This example illustrates how to use the `fflush' function
without regard to the return value:
() = fputs ("Enter value> ", stdout);
() = fflush (stdout);
SEE ALSO
fopen, fclose
--------------------------------------------------------------
fgets
SYNOPSIS
Read a line from a file
USAGE
Integer_Type fgets (SLang_Ref_Type ref, File_Type fp)
DESCRIPTION
`fgets' reads a line from the open file specified by `fp'
and places the characters in the variable whose reference is
specified by `ref'.
It returns -1 if `fp' is not associated with an open file
or an attempt was made to read at the end the file; otherwise, it
returns the number of characters read.
EXAMPLE
The following example returns the lines of a file via a linked list:
define read_file (file)
{
variable buf, fp, root, tail;
variable list_type = struct { text, next };
root = NULL;
fp = fopen(file, "r");
if (fp == NULL)
error("fopen %s failed." file);
while (-1 != fgets (&buf, fp))
{
if (root == NULL)
{
root = @list_type;
tail = root;
}
else
{
tail.next = @list_type;
tail = tail.next;
}
tail.text = buf;
tail.next = NULL;
}
() = fclose (fp);
return root;
}
SEE ALSO
fgetslines, fopen, fclose, fputs, fread, error
--------------------------------------------------------------
fgetslines
SYNOPSIS
Read lines as an array from an open file
USAGE
String_Type[] fgetslines (File_Type fp [,Int_Type num])
DESCRIPTION
The `fgetslines' function reads lines a specified number of
lines as an array of strings from the file associated with the
file pointer `fp'. If the number of lines to be read is left
unspecified, the function will return the rest of the lines in the
file. If the file is empty, an empty string array will be returned.
The function returns NULL upon error.
EXAMPLE
The following function returns the number of lines in a file:
define count_lines_in_file (file)
{
variable fp, lines;
fp = fopen (file, "r");
if (fp == NULL)
return -1;
lines = fgetslines (fp);
if (lines == NULL)
return -1;
return length (lines);
}
Note that the file was implicitly closed when the variable `fp'
goes out of scope (in the case, when the function returns).
SEE ALSO
fgets, fread, fopen, fputslines
--------------------------------------------------------------
fopen
SYNOPSIS
Open a file
USAGE
File_Type fopen (String_Type f, String_Type m)
DESCRIPTION
The `fopen' function opens a file `f' according to the mode
string `m'. Allowed values for `m' are:
"r" Read only
"w" Write only
"a" Append
"r+" Reading and writing at the beginning of the file.
"w+" Reading and writing. The file is created if it does not
exist; otherwise, it is truncated.
"a+" Reading and writing at the end of the file. The file is created
if it does not already exist.
In addition, the mode string can also include the letter `'b''
as the last character to indicate that the file is to be opened in
binary mode.
Upon success, `fopen' returns a File_Type object which is
meant to be used by other operations that require an open file
pointer. Upon failure, the function returns NULL.
EXAMPLE
The following function opens a file in append mode and writes a
string to it:
define append_string_to_file (file, str)
{
variable fp = fopen (file, "a");
if (fp == NULL)
throw OpenError, "$file could not be opened"$;
() = fputs (string, fp);
() = fclose (fp);
}
Note that the return values from `fputs' and `fclose' were
ignored.
NOTES
There is no need to explicitly close a file opened with `fopen'.
If the returned File_Type object goes out of scope, the
interpreter will automatically close the file. However, explicitly
closing a file with `fclose' and checking its return value is
recommended.
SEE ALSO
fclose, fgets, fputs, popen
--------------------------------------------------------------
fprintf
SYNOPSIS
Create and write a formatted string to a file
USAGE
Int_Type fprintf (File_Type fp, String_Type fmt, ...)
DESCRIPTION
`fprintf' formats the objects specified by the variable argument
list according to the format `fmt' and write the result to the
open file pointer `fp'.
The format string obeys the same syntax and semantics as the
`sprintf' format string. See the description of the
`sprintf' function for more information.
`fprintf' returns the number of bytes written to the file,
or -1 upon error.
SEE ALSO
fputs, printf, fwrite, message
--------------------------------------------------------------
fputs
SYNOPSIS
Write a string to an open stream
USAGE
Integer_Type fputs (String_Type s, File_Type fp)
DESCRIPTION
The `fputs' function writes the string `s' to the open file
pointer `fp'. It returns -1 upon failure and sets `errno',
otherwise it returns the length of the string.
EXAMPLE
The following function opens a file in append mode and uses the
`fputs' function to write to it.
define append_string_to_file (str, file)
{
variable fp;
fp = fopen (file, "a");
if (fp == NULL)
throw OpenError, "Unable to open $file"$;
if ((-1 == fputs (s, fp))
or (-1 == fclose (fp)))
throw WriteError, "Error writing to $file";
}
NOTES
One must not disregard the return value from the `fputs'
function. Doing so may lead to a stack overflow error.
To write an object that contains embedded null characters, use the
`fwrite' function.
SEE ALSO
fclose, fopen, fgets, fwrite
--------------------------------------------------------------
fputslines
SYNOPSIS
Write an array of strings to an open file
USAGE
Int_Type fputslines (String_Type[]a, File_Type fp)
DESCRIPTION
The `fputslines' function writes an array of strings to the
specified file pointer. It returns the number of elements
successfully written. Any NULL elements in the array will be
skipped.
EXAMPLE
if (length (lines) != fputslines (fp, lines))
throw WriteError;
SEE ALSO
fputs, fgetslines, fopen
--------------------------------------------------------------
fread
SYNOPSIS
Read binary data from a file
USAGE
UInt_Type fread (Ref_Type b, DataType_Type t, UInt_Type n, File_Type fp)
DESCRIPTION
The `fread' function may be used to read `n' objects of type
`t' from an open file pointer `fp'. Upon success, it
returns the number of objects read from the file and places the
objects in variable specified by `b'. Upon error or
end-of-file, it returns -1 and sets `errno' accordingly.
If more than one object is read from the file, those objects will be
placed in an array of the appropriate size.
EXAMPLE
The following example illustrates how to read 50 integers from a file:
define read_50_ints_from_a_file (file)
{
variable fp, n, buf;
fp = fopen (file, "rb");
if (fp == NULL)
throw OpenError;
n = fread (&buf, Int_Type, 50, fp);
if (n == -1)
throw ReadError, "fread failed";
() = fclose (fp);
return buf;
}
NOTES
Use the `pack' and `unpack' functions to read data with a
specific byte-ordering.
The `fread_bytes' function may be used to read a specified number of
bytes in the form of a binary string (`BString_Type').
SEE ALSO
fread_bytes, fwrite, fgets, fopen, pack, unpack
--------------------------------------------------------------
fread_bytes
SYNOPSIS
Read bytes from a file as a binary-string
USAGE
UInt_Type fread_bytes (Ref_Type b, UInt_Type n, File_Type fp)
DESCRIPTION
The `fread_bytes' function may be used to read `n' bytes
from from an open file pointer `fp'. Upon success, it returns
the number of bytes read from the file and assigns to the variable
attached to the reference `b' a binary string formed from the
bytes read. Upon error or end of file, the function returns
-1 and sets `errno' accordingly.
NOTES
Use the `pack' and `unpack' functions to read data with a
specific byte-ordering.
SEE ALSO
fread, fwrite, fgets, fopen, pack, unpack
--------------------------------------------------------------
fseek
SYNOPSIS
Reposition a stdio stream
USAGE
Integer_Type fseek (File_Type fp, LLong_Type ofs, Integer_Type whence
DESCRIPTION
The `fseek' function may be used to reposition the file position
pointer associated with the open file stream `fp'. Specifically,
it moves the pointer `ofs' bytes relative to the position
indicated by `whence'. If `whence' is set to one of the symbolic
constants SEEK_SET, SEEK_CUR, or SEEK_END, the
offset is relative to the start of the file, the current position
indicator, or end-of-file, respectively.
The function returns 0 upon success, or -1 upon failure and sets
`errno' accordingly.
EXAMPLE
define rewind (fp)
{
if (0 == fseek (fp, 0, SEEK_SET)) return;
vmessage ("rewind failed, reason: %s", errno_string (errno));
}
SEE ALSO
ftell, fopen
--------------------------------------------------------------
ftell
SYNOPSIS
Obtain the current position in an open stream
USAGE
LLong_Type ftell (File_Type fp)
DESCRIPTION
The ftell function may be used to obtain the current position in the
stream associated with the open file pointer `fp'. It returns
the position of the pointer measured in bytes from the beginning of
the file. Upon error, it returns `-1' and sets `errno'
accordingly.
SEE ALSO
fseek, fopen
--------------------------------------------------------------
fwrite
SYNOPSIS
Write binary data to a file
USAGE
UInt_Type fwrite (b, File_Type fp)
DESCRIPTION
The `fwrite' function may be used to write the object represented by
`b' to an open file. If `b' is a string or an array, the
function will attempt to write all elements of the object to the
file. It returns the number of elements successfully written,
otherwise it returns -1 upon error and sets `errno'
accordingly.
EXAMPLE
The following example illustrates how to write an integer array to a
file. In this example, `fp' is an open file descriptor:
variable a = [1:50]; % 50 element integer array
if (50 != fwrite (a, fp))
throw WriteError;
Here is how to write the array one element at a time:
variable ai, a = [1:50];
foreach ai (a)
{
if (1 != fwrite(ai, fp))
throw WriteError;
}
NOTES
Not all data types may be supported the `fwrite' function. It
is supported by all vector, scalar, and string objects.
SEE ALSO
fread, fputs, fopen, pack, unpack
--------------------------------------------------------------
pclose
SYNOPSIS
Close a process pipe
USAGE
Integer_Type pclose (File_Type fp)
DESCRIPTION
The `pclose' function waits for the process associated with
`fp' to exit and the returns the exit status of the command.
SEE ALSO
pclose, fclose
--------------------------------------------------------------
popen
SYNOPSIS
Open a pipe to a process
USAGE
File_Type popen (String_Type cmd, String_Type mode)
DESCRIPTION
The `popen' function executes a process specified by `cmd'
and opens a unidirectional pipe to the newly created process. The
`mode' indicates whether or not the pipe is open for reading
or writing. Specifically, if `mode' is `"r"', then the
pipe is opened for reading, or if `mode' is `"w"', then the
pipe will be open for writing.
Upon success, a File_Type pointer will be returned, otherwise
the function failed and NULL will be returned.
NOTES
This function is not available on all systems.
SEE ALSO
pclose, fopen
--------------------------------------------------------------
printf
SYNOPSIS
Create and write a formatted string to stdout
USAGE
Int_Type printf (String_Type fmt, ...)
DESCRIPTION
`printf' formats the objects specified by the variable argument
list according to the format `fmt' and write the result to
`stdout'. This function is equivalent to `fprintf' used
with the `stdout' file pointer. See `fprintf' for more
information.
`printf' returns the number of bytes written or -1 upon error.
NOTES
Many C programmers do not check the return status of the
`printf' C library function. Make sure that if you do not care
about whether or not the function succeeds, then code it as in the
following example:
() = printf ("%s laid %d eggs\n", chicken_name, num_egg);
SEE ALSO
fputs, printf, fwrite, message
--------------------------------------------------------------
create_delimited_string
SYNOPSIS
Concatenate strings using a delimiter
USAGE
String_Type create_delimited_string (delim, s_1, s_2, ..., s_n, n)
String_Type delim, s_1, ..., s_n
Int_Type n
DESCRIPTION
`create_delimited_string' performs a concatenation operation on
the `n' strings `s_1', ...,`s_n', using the string
`delim' as a delimiter. The resulting string is equivalent to
one obtained via
s_1 + delim + s_2 + delim + ... + s_n
EXAMPLE
create_delimited_string ("/", "user", "local", "bin", 3);
will produce `"usr/local/bin"'.
NOTES
New code should use the `strjoin' function, which performs a
similar task.
SEE ALSO
strjoin, is_list_element, extract_element, strchop, strcat
--------------------------------------------------------------
extract_element
SYNOPSIS
Extract the nth element of a string with delimiters
USAGE
String_Type extract_element (String_Type list, Int_Type nth, Int_Type delim)
DESCRIPTION
The `extract_element' function may be used to extract the
`nth' substring of a string delimited by the character given by
the `delim' parameter. If the string contains fewer than the
requested substring, the function will return NULL. Substring
elements are numbered from 0.
EXAMPLE
The expression
extract_element ("element 0, element 1, element 2", 1, ',')
returns the string `" element 1"', whereas
extract_element ("element 0, element 1, element 2", 1, ' ')
returns `"0,"'.
The following function may be used to compute the number of elements
in the list:
define num_elements (list, delim)
{
variable nth = 0;
while (NULL != extract_element (list, nth, delim))
nth++;
return nth;
}
Alternatively, the `strchop' function may be more useful. In
fact, `extract_element' may be expressed in terms of the
function `strchop' as
define extract_element (list, nth, delim)
{
list = strchop(list, delim, 0);
if (nth >= length (list))
return NULL;
else
return list[nth];
}
and the `num_elements' function used above may be recoded more
simply as:
define num_elements (list, delim)
{
return length (strchop (length, delim, 0));
}
NOTES
New code should make use of the `List_Type' object for lists.
SEE ALSO
is_list_element, is_substr, strtok, strchop, create_delimited_string
--------------------------------------------------------------
glob_to_regexp
SYNOPSIS
Convert a globbing expression to a regular expression
USAGE
String_Type glob_to_regexp (String_Type g)
DESCRIPTION
This function may be used to convert a so-called globbing expression
to a regular expression. A globbing expression is frequently used
for matching filenames where '?' represents a single character and
'*' represents 0 or more characters.
NOTES
The `slsh' program that is distributed with the S-Lang library
includes a function called `glob' that is a wrapper around
`glob_to_regexp' and `listdir'. It returns a list of
filenames matching a globbing expression.
SEE ALSO
string_match, listdir
--------------------------------------------------------------
is_list_element
SYNOPSIS
Test whether a delimited string contains a specific element
USAGE
Int_Type is_list_element (String_Type list, String_Type elem, Int_Type delim)
DESCRIPTION
The `is_list_element' function may be used to determine whether
or not a delimited list of substring, `list', contains the element
`elem'. If `elem' is not an element of `list', the function
will return zero, otherwise, it returns 1 plus the matching element
number.
EXAMPLE
The expression
is_list_element ("element 0, element 1, element 2", "0,", ' ');
returns `2' since `"0,"' is element number one of the list
(numbered from zero).
SEE ALSO
extract_element, is_substr, create_delimited_string
--------------------------------------------------------------
is_substr
SYNOPSIS
Test for a specified substring within a string
USAGE
Int_Type is_substr (String_Type a, String_Type b)
DESCRIPTION
This function may be used to determine if `a' contains the
string `b'. If it does not, the function returns 0; otherwise it
returns the position of the first occurrence of `b' in `a'
expressed in terms of characters, not bytes.
NOTES
This function regards the first character of a string to be given by
a position value of 1.
The distinction between characters and bytes is significant in UTF-8
mode.
SEE ALSO
substr, string_match, strreplace
--------------------------------------------------------------
make_printable_string
SYNOPSIS
Format a string suitable for parsing
USAGE
String_Type make_printable_string(String_Type str)
DESCRIPTION
This function formats a string in such a way that it may be used as
an argument to the `eval' function. The resulting string is
identical to `str' except that it is enclosed in double quotes
and the backslash, newline, control, and double quote characters are
expanded.
SEE ALSO
eval, str_quote_string
--------------------------------------------------------------
Sprintf
SYNOPSIS
Format objects into a string (deprecated)
USAGE
String_Type Sprintf (String_Type format, ..., Int_Type n)
DESCRIPTION
This function performs a similar task as the `sprintf'
function but requires an additional argument that specifies the
number of items to format. For this reason, the `sprintf'
function should be used.
SEE ALSO
sprintf, string, sscanf, vmessage
--------------------------------------------------------------
sprintf
SYNOPSIS
Format objects into a string
USAGE
String_Type sprintf (String fmt, ...)
DESCRIPTION
The `sprintf' function formats a string from a variable number
of arguments according to according to the format specification
string `fmt'.
The format string is a C library `sprintf' style format
descriptor. Briefly, the format string may consist of ordinary
characters (not including the `%' character), which are copied
into the output string as-is, and conversion specification sequences
introduced by the `%' character. The number of additional
arguments passed to the `sprintf' function must be consistent
with the number required by the format string.
The `%' character in the format string starts a conversion
specification that indicates how an object is to be formatted.
Usually the percent character is followed immediately by a
conversion specification character. However, it may optionally be
followed by flag characters, field width characters, and precision
modifiers, as described below.
The character immediately following the `%' character may be
one or more of the following flag characters:
- Use left-justification
# Use alternate form for formatting.
0 Use 0 padding
+ Preceed a number by a plus or minus sign.
(space) Use a blank instead of a plus sign.
The flag characters (if any) may be followed by an optional field
width specification string represented by one or more digit
characters. If the size of the formatted object is less than the
field width, it will be right-justified in the specified field
width, unless the `-' flag was given, in which case it will be
left justified.
If the next character in the control sequence is a period, then it
introduces a precision specification sequence. The precision is
given by the digit characters following the period. If none are
given the precision is taken to be 0. The meaning of the precision
specifier depends upon the type of conversion: For integer
conversions, it gives the minimum number digits to appear in the
output. For `e' and `f' floating point conversions, it
gives the number of digits to appear after the decimal point. For
the `g' floating point conversion, it gives the maximum number
of significant digits to appear. Finally for the `s' and
`S' conversions it specifies the maximum number of characters
to be copied to the output string.
The next character in the sequence may be a modifier that controls
the size of object to be formatted. It may consist of the following
characters:
h This character is ignored in the current implementation.
l The integer is be formatted as a long integer, or a
character as a wide character.
Finally the conversion specification sequence ends with the
conversion specification character that describes how the object is
to be
formatted:
s as a string
f as a floating point number
e as a float using exponential form, e.g., 2.345e08
g format as e or g, depending upon its value
c as a character
% a literal percent character
d as a signed decimal integer
u as an unsigned decimal integer
o as an octal integer
X as hexadecimal
S convert object to a string and format accordingly
The `S' conversion specifier is a S-Lang extension which will
cause the corresponding object to be converted to a string using the
`string' function, and then converted as `s'. formatted as
string. In fact, `sprintf("%S",x)' is equivalent to
`sprintf("%s",string(x))'.
EXAMPLE
sprintf("%s","hello") ===> "hello"
sprintf("%s %s","hello", "world") ===> "hello world"
sprintf("Agent %.3d",7) ===> "Agent 007"
sprintf("%S",PI) ===> "3.14159"
sprintf("%g",PI) ===> "3.14159"
sprintf("%.2g",PI) ===> "3.1"
sprintf("%.2e",PI) ===> "3.14e+00"
sprintf("%.2f",PI) ===> "3.14"
sprintf("|% 8.2f|",PI) ===> "| 3.14|"
sprintf("|%-8.2f|",PI) ===> "|3.14 |"
sprintf("|%+8.2f|",PI) ===> "| +3.14|"
sprintf("%S",{1,2,3}) ===> "List_Type with 3 elements"
sprintf("%S",1+2i) ===> "(1 + 2i)"
NOTES
The `set_float_format' function controls the format for the
`S' conversion of floating point numbers.
SEE ALSO
string, sscanf, message
--------------------------------------------------------------
sscanf
SYNOPSIS
Parse a formatted string
USAGE
Int_Type sscanf (s, fmt, r1, ... rN)
String_Type s, fmt;
Ref_Type r1, ..., rN
DESCRIPTION
The `sscanf' function parses the string `s' according to the
format `fmt' and sets the variables whose references are given by
`r1', ..., `rN'. The function returns the number of
references assigned, or throws an exception upon error.
The format string `fmt' consists of ordinary characters and
conversion specifiers. A conversion specifier begins with the
special character `%' and is described more fully below. A white
space character in the format string matches any amount of whitespace
in the input string. Parsing of the format string stops whenever a
match fails.
The `%' character is used to denote a conversion specifier whose
general form is given by `%[*][width][type]format' where the
brackets indicate optional items. If `*' is present, then the
conversion will be performed but no assignment to a reference will be
made. The `width' specifier specifies the maximum field width to
use for the conversion. The `type' modifier is used to indicate
the size of the object, e.g., a short integer, as follows.
If _type_ is given as the character `h', then if the format
conversion is for an integer (`dioux'), the object assigned will
be a short integer. If _type_ is `l', then the conversion
will be to a long integer for integer conversions, or to a double
precision floating point number for floating point conversions.
The format specifier is a character that specifies the conversion:
% Matches a literal percent character. No assignment is
performed.
d Matches a signed decimal integer.
D Matches a long decimal integer (equiv to `ld')
u Matches an unsigned decimal integer
U Matches an unsigned long decimal integer (equiv to `lu')
i Matches either a hexadecimal integer, decimal integer, or
octal integer.
I Equivalent to `li'.
x Matches a hexadecimal integer.
X Matches a long hexadecimal integer (same as `lx').
e,f,g Matches a decimal floating point number (Float_Type).
E,F,G Matches a double precision floating point number, same as `lf'.
s Matches a string of non-whitespace characters (String_Type).
c Matches one character. If width is given, width
characters are matched.
n Assigns the number of characters scanned so far.
[...] Matches zero or more characters from the set of characters
enclosed by the square brackets. If '^' is given as the
first character, then the complement set is matched.
EXAMPLE
Suppose that `s' is `"Coffee: (3,4,12.4)"'. Then
n = sscanf (s, "%[a-zA-Z]: (%d,%d,%lf)", &item, &x, &y, &z);
will set `n' to 4, `item' to `"Coffee"', `x' to 3,
`y' to 4, and `z' to the double precision number
`12.4'. However,
n = sscanf (s, "%s: (%d,%d,%lf)", &item, &x, &y, &z);
will set `n' to 1, `item' to `"Coffee:"' and the
remaining variables will not be assigned.
SEE ALSO
sprintf, unpack, string, atof, int, integer, string_match
--------------------------------------------------------------
strbytelen
SYNOPSIS
Get the number of bytes in a string
USAGE
Int_Type strbytelen (String_Type s)
DESCRIPTION
This function returns the number of bytes in a string. In UTF-8
mode, this value is generally different from the number of
characters in a string. For the latter information, the
`strlen' or `strcharlen' functions should be used.
SEE ALSO
strlen, strcharlen, length
--------------------------------------------------------------
strbytesub
SYNOPSIS
Replace a byte with another in a string.
USAGE
String_Type strsub (String_Type s, Int_Type pos, UChar_Type b)
DESCRIPTION
The `strbytesub' function may be be used to substitute the byte
`b' for the byte at byte position `pos' of the string
`s'. The resulting string is returned.
NOTES
The first byte in the string `s' is specified by `pos'
equal to 1. This function uses byte semantics, not character
semantics.
SEE ALSO
strsub, is_substr, strreplace, strbytelen
--------------------------------------------------------------
strcat
SYNOPSIS
Concatenate strings
USAGE
String_Type strcat (String_Type a_1, ..., String_Type a_N)
DESCRIPTION
The `strcat' function concatenates its N string
arguments `a_1', ... `a_N' together and returns the result.
EXAMPLE
strcat ("Hello", " ", "World");
produces the string `"Hello World"'.
NOTES
This function is equivalent to the binary operation `a_1+...+a_N'.
However, `strcat' is much faster making it the preferred method
to concatenate strings.
SEE ALSO
sprintf, strjoin
--------------------------------------------------------------
strcharlen
SYNOPSIS
Get the number of characters in a string including combining characters
USAGE
Int_Type strcharlen (String_Type s)
DESCRIPTION
The `strcharlen' function returns the number of characters in a
string. If the string contains combining characters, then they are
also counted. Use the `strlen' function to obtain the
character count ignoring combining characters.
SEE ALSO
strlen, strbytelen
--------------------------------------------------------------
strchop
SYNOPSIS
Chop or split a string into substrings.
USAGE
String_Type[] strchop (String_Type str, Int_Type delim, Int_Type quote)
DESCRIPTION
The `strchop' function may be used to split-up a string
`str' that consists of substrings delimited by the character
specified by `delim'. If the integer `quote' is non-zero,
it will be taken as a quote character for the delimiter. The
function returns the substrings as an array.
EXAMPLE
The following function illustrates how to sort a comma separated
list of strings:
define sort_string_list (a)
{
variable i, b, c;
b = strchop (a, ',', 0);
i = array_sort (b);
b = b[i]; % rearrange
% Convert array back into comma separated form
return strjoin (b, ",");
}
SEE ALSO
strchopr, strjoin, strtok
--------------------------------------------------------------
strchopr
SYNOPSIS
Chop or split a string into substrings.
USAGE
String_Type[] strchopr (String_Type str, String_Type delim, String_Type quote)
DESCRIPTION
This routine performs exactly the same function as `strchop' except
that it returns the substrings in the reverse order. See the
documentation for `strchop' for more information.
SEE ALSO
strchop, strtok, strjoin
--------------------------------------------------------------
strcmp
SYNOPSIS
Compare two strings
USAGE
Int_Type strcmp (String_Type a, String_Type b)
DESCRIPTION
The `strcmp' function may be used to perform a case-sensitive
string comparison, in the lexicographic sense, on strings `a' and
`b'. It returns 0 if the strings are identical, a negative integer
if `a' is less than `b', or a positive integer if `a' is greater
than `b'.
EXAMPLE
The `strup' function may be used to perform a case-insensitive
string comparison:
define case_insensitive_strcmp (a, b)
{
return strcmp (strup(a), strup(b));
}
NOTES
One may also use one of the binary comparison operators, e.g.,
`a > b'.
SEE ALSO
strup, strncmp
--------------------------------------------------------------
strcompress
SYNOPSIS
Remove excess whitespace characters from a string
USAGE
String_Type strcompress (String_Type s, String_Type white)
DESCRIPTION
The `strcompress' function compresses the string `s' by
replacing a sequence of one or more characters from the set
`white' by the first character of `white'. In addition, it
also removes all leading and trailing characters from `s' that
are part of `white'.
EXAMPLE
The expression
strcompress (",;apple,,cherry;,banana", ",;");
returns the string `"apple,cherry,banana"'.
SEE ALSO
strtrim, strtrans, str_delete_chars
--------------------------------------------------------------
string_match
SYNOPSIS
Match a string against a regular expression
USAGE
Int_Type string_match(String_Type str, String_Type pat, Int_Type nth)
DESCRIPTION
The `string_match' function returns zero if `str' does not
match regular expression specified by `pat'. This function
performs the match starting at the `nth' byte in the string
`str' (numbered from 1). This function returns the position in
bytes (numbered from 1) of the start of the match in `str'.
The exact substring matched may be found using
`string_match_nth'.
NOTES
Positions in the string are specified using byte-offsets not
character offsets. The value returned by this function is measured
from the beginning of the string `str'.
The function is not yet UTF-8 aware. If possible, consider using
the `pcre' module for better, more sophisticated regular
expressions.
SEE ALSO
string_match_nth, strcmp, strncmp
--------------------------------------------------------------
string_match_nth
SYNOPSIS
Get the result of the last call to string_match
USAGE
(Int_Type pos, Int_Type len) = string_match_nth(Int_Type nth)
DESCRIPTION
The `string_match_nth' function returns two integers describing
the result of the last call to `string_match'. It returns both
the zero-based byte-position of the `nth' submatch and
the length of the match.
By convention, `nth' equal to zero means the entire match.
Otherwise, `nth' must be an integer with a value 1 through 9,
and refers to the set of characters matched by the `nth' regular
expression enclosed by the pairs `\(, \)'.
EXAMPLE
Consider:
variable matched, pos, len;
matched = string_match("hello world", "\([a-z]+\) \([a-z]+\)"R, 1);
if (matched)
(pos, len) = string_match_nth(2);
This will set `matched' to 1 since a match will be found at the
first byte position, `pos' to 6 since `w' is offset 6 bytes
from the beginning of the string, and `len' to 5 since
`"world"' is 5 bytes long.
NOTES
The position offset is _not_ affected by the value of the offset
parameter to the `string_match' function. For example, if the
value of the last parameter to the `string_match' function had
been 3, `pos' would still have been set to 6.
SEE ALSO
string_match
--------------------------------------------------------------
strjoin
SYNOPSIS
Concatenate elements of a string array
USAGE
String_Type strjoin (Array_Type a, String_Type delim)
DESCRIPTION
The `strjoin' function operates on an array of strings by joining
successive elements together separated with a delimiter `delim'.
If `delim' is the empty string `""', then the result will
simply be the concatenation of the elements.
EXAMPLE
Suppose that
days = ["Sun","Mon","Tue","Wed","Thu","Fri","Sat","Sun"];
Then `strjoin (days,"+")' will produce
`"Sun+Mon+Tue+Wed+Thu+Fri+Sat+Sun"'. Similarly,
`strjoin (["","",""], "X")' will produce `"XX"'.
SEE ALSO
strchop, strcat
--------------------------------------------------------------
strlen
SYNOPSIS
Compute the length of a string
USAGE
Int_Type strlen (String_Type a)
DESCRIPTION
The `strlen' function may be used to compute the character
length of a string ignoring the presence of combining characters.
The `strcharlen' function may be used to count combining
characters as distinct characters. For byte-semantics, use the
`strbytelen' function.
EXAMPLE
After execution of
variable len = strlen ("hello");
`len' will have a value of `5'.
SEE ALSO
strbytelen, strcharlen, bstrlen, length, substr
--------------------------------------------------------------
strlow
SYNOPSIS
Convert a string to lowercase
USAGE
String_Type strlow (String_Type s)
DESCRIPTION
The `strlow' function takes a string `s' and returns another
string identical to `s' except that all upper case characters
that are contained in `s' are converted converted to lower case.
EXAMPLE
The function
define Strcmp (a, b)
{
return strcmp (strlow (a), strlow (b));
}
performs a case-insensitive comparison operation of two strings by
converting them to lower case first.
SEE ALSO
strup, tolower, strcmp, strtrim, define_case
--------------------------------------------------------------
strnbytecmp
SYNOPSIS
Compare the first n bytes of two strings
USAGE
Int_Type strnbytecmp (String_Type a, String_Type b, Int_Type n)
DESCRIPTION
This function compares the first `n' bytes of the strings
`a' and `b'. See the documentation for `strcmp' for
information about the return value.
SEE ALSO
strncmp, strncharcmp, strcmp
--------------------------------------------------------------
strncharcmp
SYNOPSIS
Compare the first n characters of two strings
USAGE
Int_Type strncharcmp (String_Type a, String_Type b, Int_Type n)
DESCRIPTION
This function compares the first `n' characters of the strings
`a' and `b' counting combining characters as distinct
characters. See the documentation for `strcmp' for information
about the return value.
SEE ALSO
strncmp, strnbytecmp, strcmp
--------------------------------------------------------------
strncmp
SYNOPSIS
Compare the first few characters of two strings
USAGE
Int_Type strncmp (String_Type a, String_Type b, Int_Type n)
DESCRIPTION
This function behaves like `strcmp' except that it compares only the
first `n' characters in the strings `a' and `b'.
See the documentation for `strcmp' for information about the return
value.
In counting characters, combining characters are not counted,
although they are used in the comparison. Use the
`strncharcmp' function if you want combining characters to be
included in the character count. The `strnbytecmp' function
should be used to compare bytes.
EXAMPLE
The expression
strcmp ("apple", "appliance", 3);
will return zero since the first three characters match.
NOTES
This function uses character semantics.
SEE ALSO
strcmp, strlen, strncharcmp, strnbytecmp
--------------------------------------------------------------
strreplace
SYNOPSIS
Replace one or more substrings
USAGE
(new, n) = strreplace (a, b, c, max_n)
String_Type a, b, c, rep;
Int_Type n, max_n;
DESCRIPTION
The `strreplace' function may be used to replace one or more
occurrences of `b' in `a' with `c'. If the integer
`max_n' is positive, then the first `max_n' occurrences of
`b' in `a' will be replaced. Otherwise, if `max_n' is
negative, then the last `abs(max_n)' occurrences will be replaced.
The function returns the resulting string and an integer indicating
how many replacements were made.
EXAMPLE
The following function illustrates how `strreplace' may be used
to remove all occurrences of a specified substring:
define delete_substrings (a, b)
{
(a, ) = strreplace (a, b, "", strlen (a));
return a;
}
SEE ALSO
is_substr, strsub, strtrim, strtrans, str_delete_chars
--------------------------------------------------------------
strsub
SYNOPSIS
Replace a character with another in a string.
USAGE
String_Type strsub (String_Type s, Int_Type pos, Int_Type ch)
DESCRIPTION
The `strsub' function may be used to substitute the character
`ch' for the character at character position `pos' of the string
`s'. The resulting string is returned.
EXAMPLE
define replace_spaces_with_comma (s)
{
variable n;
while (n = is_substr (s, " "), n) s = strsub (s, n, ',');
return s;
}
For uses such as this, the `strtrans' function is a better choice.
NOTES
The first character in the string `s' is specified by `pos'
equal to 1. This function uses character semantics, not byte
semantics.
SEE ALSO
is_substr, strreplace, strlen
--------------------------------------------------------------
strtok
SYNOPSIS
Extract tokens from a string
USAGE
String_Type[] strtok (String_Type str [,String_Type white])
DESCRIPTION
`strtok' breaks the string `str' into a series of tokens
and returns them as an array of strings. If the second parameter
`white' is present, then it specifies the set of characters
that are to be regarded as whitespace when extracting the tokens,
and may consist of the whitespace characters or a range of such
characters. If the first character of `white' is `'^'',
then the whitespace characters consist of all characters except
those in `white'. For example, if `white' is `"
\t\n,;."', then those characters specify the whitespace
characters. However, if `white' is given by
`"^a-zA-Z0-9_"', then any character is a whitespace character
except those in the ranges `a-z', `A-Z', `0-9', and
the underscore character. To specify the hyphen character as a
whitespace character, then it should be the first character of the
whitespace string. In addition to ranges, the whitespace specifier
may also include character classes:
\w matches a unicode "word" character, taken to be alphanumeric.
\a alphabetic character, excluding digits
\s matches whitespace
\l matches lowercase
\u matches uppercase
\d matches a digit
\\ matches a backslash
\^ matches a ^ character
If the second parameter is not present, then it defaults to
`"\s"'.
EXAMPLE
The following example may be used to count the words in a text file:
define count_words (file)
{
variable fp, line, count;
fp = fopen (file, "r");
if (fp == NULL) return -1;
count = 0;
while (-1 != fgets (&line, fp))
{
line = strtok (line, "^\\a");
count += length (line);
}
() = fclose (fp);
return count;
}
Here a word was assumed to consist only of alphabetic characters.
SEE ALSO
strchop, strcompress, strjoin
--------------------------------------------------------------
strtrans
SYNOPSIS
Replace characters in a string
USAGE
String_Type strtrans (str, old_set, new_set)
String_Type str, old_set, new_set;
DESCRIPTION
The `strtrans' function may be used to replace all the characters
from the set `old_set' with the corresponding characters from
`new_set' in the string `str'. If `new_set' is empty,
then the characters in `old_set' will be removed from `str'.
If `new_set' is not empty, then `old_set' and
`new_set' must be commensurate. Each set may consist of
character ranges such as `A-Z' and character classes:
\w matches a unicode "word" character, taken to be alphanumeric.
\a alphabetic character, excluding digits
\s matches whitespace
\l matches lowercase
\u matches uppercase
\d matches a digit
\\ matches a backslash
\^ matches a ^ character
If the first character of a set is `^' then the set is taken to
be the complement set.
EXAMPLE
str = strtrans (str, "\\u", "\\l"); % lower-case str
str = strtrans (str, "^0-9", " "); % Replace anything but 0-9 by space
str = strtrans (str, "\\^0-9", " "); % Replace '^' and 0-9 by a space
SEE ALSO
strreplace, strtrim, strup, strlow
--------------------------------------------------------------
strtrim
SYNOPSIS
Remove whitespace from the ends of a string
USAGE
String_Type strtrim (String_Type s [,String_Type w])
DESCRIPTION
The `strtrim' function removes all leading and trailing whitespace
characters from the string `s' and returns the result. The
optional second parameter specifies the set of whitespace
characters. If the argument is not present, then the set defaults
to `"\s"'. The whitespace specification may consist of
character ranges such as `A-Z' and character classes:
\w matches a unicode "word" character, taken to be alphanumeric.
\a alphabetic character, excluding digits
\s matches whitespace
\l matches lowercase
\u matches uppercase
\d matches a digit
\\ matches a backslash
\^ matches a ^ character
If the first character of a set is `^' then the set is taken to
be the complement set.
SEE ALSO
strtrim_beg, strtrim_end, strcompress
--------------------------------------------------------------
strtrim_beg
SYNOPSIS
Remove leading whitespace from a string
USAGE
String_Type strtrim_beg (String_Type s [,String_Type w])
DESCRIPTION
The `strtrim_beg' function removes all leading whitespace
characters from the string `s' and returns the result.
The optional second parameter specifies the set of whitespace
characters. See the documentation for the `strtrim' function
form more information about the whitespace parameter.
SEE ALSO
strtrim, strtrim_end, strcompress
--------------------------------------------------------------
strtrim_end
SYNOPSIS
Remove trailing whitespace from a string
USAGE
String_Type strtrim_end (String_Type s [,String_Type w])
DESCRIPTION
The `strtrim_end' function removes all trailing whitespace
characters from the string `s' and returns the result. The
optional second parameter specifies the set of whitespace
characters. See the documentation for the `strtrim' function
form more information about the whitespace parameter.
SEE ALSO
strtrim, strtrim_beg, strcompress
--------------------------------------------------------------
strup
SYNOPSIS
Convert a string to uppercase
USAGE
String_Type strup (String_Type s)
DESCRIPTION
The `strup' function takes a string `s' and returns another
string identical to `s' except that all lower case characters
that contained in `s' are converted to upper case.
EXAMPLE
The function
define Strcmp (a, b)
{
return strcmp (strup (a), strup (b));
}
performs a case-insensitive comparison operation of two strings by
converting them to upper case first.
SEE ALSO
strlow, toupper, strcmp, strtrim, define_case, strtrans
--------------------------------------------------------------
str_delete_chars
SYNOPSIS
Delete characters from a string
USAGE
String_Type str_delete_chars (String_Type str, String_Type del_set
DESCRIPTION
This function may be used to delete the set of characters specified
by `del_set' from the string `str'. The result is returned.
The set of characters to be deleted may include ranges such as
`A-Z' and characters classes:
\w matches a unicode "word" character, taken to be alphanumeric.
\a alphabetic character, excluding digits
\s matches whitespace
\l matches lowercase
\u matches uppercase
\d matches a digit
\\ matches a backslash
\^ matches a ^ character
If the first character of `del_set' is `^', then the set
is taken to be the complement of the remaining string.
EXAMPLE
str = str_delete_chars (str, "^A-Za-z");
will remove all characters except `A-Z' and `a-z' from
`str'. Similarly,
str = str_delete_chars (str, "^\\a");
will remove all but the alphabetic characters.
SEE ALSO
strtrans, strreplace, strcompress
--------------------------------------------------------------
str_quote_string
SYNOPSIS
Escape characters in a string.
USAGE
String_Type str_quote_string(String_Type str, String_Type qlis, Int_Type quote)
DESCRIPTION
The `str_quote_string' returns a string identical to `str'
except that all characters contained in the string `qlis' are
escaped with the `quote' character, including the quote
character itself. This function is useful for making a string that
can be used in a regular expression.
EXAMPLE
Execution of the statements
node = "Is it [the coat] really worth $100?";
tag = str_quote_string (node, "\\^$[]*.+?", '\\');
will result in `tag' having the value:
Is it \[the coat\] really worth \$100\?
SEE ALSO
str_uncomment_string, make_printable_string
--------------------------------------------------------------
str_replace
SYNOPSIS
Replace a substring of a string (deprecated)
USAGE
Int_Type str_replace (String_Type a, String_Type b, String_Type c)
DESCRIPTION
The `str_replace' function replaces the first occurrence of `b' in
`a' with `c' and returns an integer that indicates whether a
replacement was made. If `b' does not occur in `a', zero is
returned. However, if `b' occurs in `a', a non-zero integer is
returned as well as the new string resulting from the replacement.
NOTES
This function has been superceded by `strreplace'. It should no
longer be used.
SEE ALSO
strreplace
--------------------------------------------------------------
str_uncomment_string
SYNOPSIS
Remove comments from a string
USAGE
String_Type str_uncomment_string(String_Type s, String_Type beg, String_Type end)
DESCRIPTION
This function may be used to remove simple forms of comments from a
string `s'. The parameters, `beg' and `end', are strings
of equal length whose corresponding characters specify the begin and
end comment characters, respectively. It returns the uncommented
string.
EXAMPLE
The expression
str_uncomment_string ("Hello (testing) 'example' World", "'(", "')")
returns the string `"Hello World"'.
NOTES
This routine does not handle multicharacter comment delimiters and it
assumes that comments are not nested.
SEE ALSO
str_quote_string, str_delete_chars, strtrans
--------------------------------------------------------------
substr
SYNOPSIS
Extract a substring from a string
USAGE
String_Type substr (String_Type s, Int_Type n, Int_Type len)
DESCRIPTION
The `substr' function returns a substring with character length
`len' of the string `s' beginning at the character position
`n'. If `len' is `-1', the entire length of the string
`s' will be used for `len'. The first character of `s'
is given by `n' equal to 1.
EXAMPLE
substr ("To be or not to be", 7, 5);
returns `"or no"'
NOTES
In many cases it is more convenient to use array indexing rather
than the `substr' function. In fact, if UTF-8 mode is not in
effect, `substr(s,i+1,strlen(s))' is equivalent to
`s[[i:]]'. Array indexing uses byte-semantics, not character
semantics assumed by the `substr' function.
SEE ALSO
is_substr, substrbytes, strlen
--------------------------------------------------------------
substrbytes
SYNOPSIS
Extract a byte sequence from a string
USAGE
String_Type substrbytes (String_Type s, Int_Type n, Int_Type len)
DESCRIPTION
The `substrbytes' function returns a substring with byte length
`len' of the string `s' beginning at the byte position
`n', counting from 1. If `len' is `-1', the entire
byte-length of the string `s' will be used for `len'. The first
byte of `s' is given by `n' equal to 1.
EXAMPLE
substrbytes ("To be or not to be", 7, 5);
returns `"or no"'
NOTES
In many cases it is more convenient to use array indexing rather
than the `substr' function. In fact
`substrbytes(s,i+1,-1)' is equivalent to
`s[[i:]]'.
The function `substr' may be used if character semantics are
desired.
SEE ALSO
substr, strbytelen
--------------------------------------------------------------
__add_binary
SYNOPSIS
Extend a binary operation to a user defined type
USAGE
__add_binary(op, return_type, binary_funct, lhs_type, rhs_type)
String_Type op;
Ref_Type binary_funct;
DataType_Type return_type, lhs_type, rhs_type;
DESCRIPTION
The `__add_binary' function is used to specify a function to be
called when a binary operation takes place between specified data
types. The first parameter indicates the binary operator and must
be one of the following:
"+", "-", "*", "/", "==", "!=", ">", ">=", "<", "<=", "^",
"or", "and", "&", "|", "xor", "shl", "shr", "mod"
The second parameter (`binary_funct') specifies the function to
be called when the binary function takes place between the
types `lhs_type' and `rhs_type'. The `return_type'
parameter stipulates the return values of the function and the data
type of the result of the binary operation.
The data type for `lhs_type' or `rhs_type' may be left
unspecified by using Any_Type for either of these values.
However, at least one of the parameters must correspond to a
user-defined datatype.
EXAMPLE
This example defines a vector data type and extends the "*" operator
to the new type:
typedef struct { x, y, z } Vector_Type;
define vector (x, y, z)
{
variable v = @Vector_Type;
v.x = x;
v.y = y;
v.z = z;
return v;
}
static define vector_scalar_mul (v, a)
{
return vector (a*v.x, a*v.y, a*v.z);
}
static define scalar_vector_mul (a, v)
{
return vector_scalar_mul (v, a);
}
static define dotprod (v1,v2)
{
return v1.x*v2.x + v1.y*v2.y + v1.z*v2.z;
}
__add_binary ("*", Vector_Type, &scalar_vector_mul, Any_Type, Vector_Type);
__add_binary ("*", Vector_Type, &scalar_vector_mul, Any_Type, Vector_Type);
__add_binary ("*", Double_Type, &dotprod, Vector_Type, Vector_Type);
SEE ALSO
__add_unary, __add_string, __add_destroy
--------------------------------------------------------------
__add_string
SYNOPSIS
Specify a string representation for a user-defined type
USAGE
__add_string (DataType_Type user_type, Ref_Type func)
DESCRIPTION
The `__add_string' function specifies a function to be called
when a string representation is required for the specified
user-defined datatype.
EXAMPLE
Consider the `Vector_Type' object defined in the example
for the `__add_binary' function.
static define vector_string (v)
{
return sprintf ("[%S,%S,%S]", v.x, v.y, v.z);
}
__add_string (Vector_Type, &vector_string);
Then
v = vector (3, 4, 5);
vmessage ("v=%S", v);
will generate the message:
v=[3,4,5]
SEE ALSO
__add_unary, __add_binary, __add_destroy, __add_typecast
--------------------------------------------------------------
__add_typecast
SYNOPSIS
Add a typecast-function for a user-defined type
USAGE
__add_typecast (DataType_Type user_type, DataType_Type totype, Ref_Type func)
DESCRIPTION
The `__add_typecast' function specifies a function to be called
to typecast the user-defined type to an object of type
`totype'. The function must be defined to take a single
argument (the user-type to be converted) and must return an object
of type `totype'.
SEE ALSO
__add_unary, __add_binary, __add_destroy, __add_string
--------------------------------------------------------------
__add_unary
SYNOPSIS
Extend a unary operator to a user-defined type
USAGE
__add_unary (op, return_type, unary_func, user_type)
String_Type op;
Ref_Type unary_func;
DataType_Type return_type, user_type;
DESCRIPTION
The `__add_unary' function is used to define the action of an
unary operation on a user-defined type. The first parameter
`op' must be a valid unary operator
"-", "not", "~"
or one of the following:
"++", "--",
"abs", "sign", "sqr", "mul2", "_ispos", "_isneg", "_isnonneg",
The third parameter, `unary_func' specifies the function to be
called to carry out the specified unary operation on the data type
`user_type'. The result of the operation is indicated by the
value of the `return_type' parameter and must also be the
return type of the unary function.
EXAMPLE
The example for the `__add_binary' function defined a
`Vector_Type' object. Here, the unary `"-"' and
`"abs"' operators are
extended to this type:
static define vector_chs (v)
{
variable v1 = @Vector_Type;
v1.x = -v.x;
v1.y = -v.y;
v1.z = -v.z;
return v1;
}
static define vector_abs (v)
{
return sqrt (v.x*v.x + v.y*v.y + v.z*v.z);
}
__add_unary ("-", Vector_Type, &vector_chs, Vector_Type);
__add_unary ("abs", Double_Type, &vector_abs, Vector_Type);
SEE ALSO
__add_binary, __add_string, __add_destroy
--------------------------------------------------------------
get_struct_field
SYNOPSIS
Get the value associated with a structure field
USAGE
x = get_struct_field (Struct_Type s, String field_name)
DESCRIPTION
The `get_struct_field' function gets the value of the field
whose name is specified by `field_name' of the structure `s'.
EXAMPLE
The following example illustrates how this function may be used to
to print the value of a structure.
define print_struct (s)
{
variable name;
foreach (get_struct_field_names (s))
{
name = ();
value = get_struct_field (s, name);
vmessage ("s.%s = %s\n", name, string(value));
}
}
SEE ALSO
set_struct_field, get_struct_field_names, array_info
--------------------------------------------------------------
get_struct_field_names
SYNOPSIS
Retrieve the field names associated with a structure
USAGE
String_Type[] = get_struct_field_names (Struct_Type s)
DESCRIPTION
The `get_struct_field_names' function returns an array of
strings whose elements specify the names of the fields of the
struct `s'.
EXAMPLE
The following example illustrates how the
`get_struct_field_names' function may be used to print the
value of a structure.
define print_struct (s)
{
variable name, value;
foreach (get_struct_field_names (s))
{
name = ();
value = get_struct_field (s, name);
vmessage ("s.%s = %s\n", name, string (value));
}
}
SEE ALSO
_push_struct_field_values, get_struct_field
--------------------------------------------------------------
is_struct_type
SYNOPSIS
Determine whether or not an object is a structure
USAGE
Integer_Type is_struct_type (X)
DESCRIPTION
The `is_struct_type' function returns 1 if the parameter
refers to a structure or a user-defined type. If the object is
neither, 0 will be returned.
SEE ALSO
typeof, _typeof, _is_struct_type
--------------------------------------------------------------
_push_struct_field_values
SYNOPSIS
Push the values of a structure's fields onto the stack
USAGE
Integer_Type num = _push_struct_field_values (Struct_Type s)
DESCRIPTION
The `_push_struct_field_values' function pushes the values of
all the fields of a structure onto the stack, returning the
number of items pushed. The fields are pushed such that the last
field of the structure is pushed first.
SEE ALSO
get_struct_field_names, get_struct_field
--------------------------------------------------------------
set_struct_field
SYNOPSIS
Set the value associated with a structure field
USAGE
set_struct_field (s, field_name, field_value)
Struct_Type s;
String_Type field_name;
Generic_Type field_value;
DESCRIPTION
The `set_struct_field' function sets the value of the field
whose name is specified by `field_name' of the structure
`s' to `field_value'.
SEE ALSO
get_struct_field, get_struct_field_names, set_struct_fields, array_info
--------------------------------------------------------------
set_struct_fields
SYNOPSIS
Set the fields of a structure
USAGE
set_struct_fields (Struct_Type s, ...)
DESCRIPTION
The `set_struct_fields' function may be used to set zero or more
fields of a structure. The fields are set in the order in which
they were created when the structure was defined.
EXAMPLE
variable s = struct { name, age, height };
set_struct_fields (s, "Bill", 13, 64);
SEE ALSO
set_struct_field, get_struct_field_names
--------------------------------------------------------------
ctime
SYNOPSIS
Convert a calendar time to a string
USAGE
String_Type ctime(Long_Type secs)
DESCRIPTION
This function returns a string representation of the time as given
by `secs' seconds since 00:00:00 UTC, Jan 1, 1970.
SEE ALSO
time, strftime, _time, localtime, gmtime
--------------------------------------------------------------
gmtime
SYNOPSIS
Break down a time in seconds to the GMT timezone
USAGE
Struct_Type gmtime (Long_Type secs)
DESCRIPTION
The `gmtime' function is exactly like `localtime' except
that the values in the structure it returns are with respect to GMT
instead of the local timezone. See the documentation for
`localtime' for more information.
NOTES
On systems that do not support the `gmtime' C library function,
this function is the same as `localtime'.
SEE ALSO
localtime, _time, mktime
--------------------------------------------------------------
localtime
SYNOPSIS
Break down a time in seconds to the local timezone
USAGE
Struct_Type localtime (Long_Type secs)
DESCRIPTION
The `localtime' function takes a parameter `secs'
representing the number of seconds since 00:00:00, January 1 1970
UTC and returns a structure containing information about `secs'
in the local timezone. The structure contains the following
Int_Type fields:
`tm_sec' The number of seconds after the minute, normally
in the range 0 to 59, but can be up to 61 to allow for
leap seconds.
`tm_min' The number of minutes after the hour, in the
range 0 to 59.
`tm_hour' The number of hours past midnight, in the range
0 to 23.
`tm_mday' The day of the month, in the range 1 to 31.
`tm_mon' The number of months since January, in the range
0 to 11.
`tm_year' The number of years since 1900.
`tm_wday' The number of days since Sunday, in the range 0
to 6.
`tm_yday' The number of days since January 1, in the
range 0 to 365.
`tm_isdst' A flag that indicates whether daylight saving
time is in effect at the time described. The value is
positive if daylight saving time is in effect, zero if it
is not, and negative if the information is not available.
SEE ALSO
gmtime, _time, ctime, mktime
--------------------------------------------------------------
mktime
SYNOPSIS
Convert a time-structure to seconds
USAGE
secs = mktime (Struct_Type tm)
DESCRIPTION
The `mktime' function is essentially the inverse of the
`localtime' function. See the documentation for that function
for more details.
SEE ALSO
localtime, gmtime, _time
--------------------------------------------------------------
strftime
SYNOPSIS
Format a date and time string
USAGE
str = strftime (String_Type format [,Struct_Type tm])
DESCRIPTION
The `strftime' creates a date and time string according to a
specified format. If called with a single argument, the current
local time will be used as the reference time. If called with two
arguments, the second argument specifies the reference time, and
must be a structure with the same fields as the structure returned
by the `localtime' function.
The format string may be composed of one or more of the following
format descriptors:
%A full weekday name (Monday)
%a abbreviated weekday name (Mon)
%B full month name (January)
%b abbreviated month name (Jan)
%c standard date and time representation
%d day-of-month (01-31)
%H hour (24 hour clock) (00-23)
%I hour (12 hour clock) (01-12)
%j day-of-year (001-366)
%M minute (00-59)
%m month (01-12)
%p local equivalent of AM or PM
%S second (00-59)
%U week-of-year, first day sunday (00-53)
%W week-of-year, first day monday (00-53)
%w weekday (0-6, sunday is 0)
%X standard time representation
%x standard date representation
%Y year with century
%y year without century (00-99)
%Z timezone name
%% percent sign
as well as any others provided by the C library. The actual values
represented by the format descriptors are locale-dependent.
EXAMPLE
message (strftime ("Today is %A, day %j of the year"));
tm = localtime (0);
message (strftime ("Unix time 0 was on a %A", tm));
SEE ALSO
localtime, time
--------------------------------------------------------------
_tic
SYNOPSIS
Reset the CPU timer
USAGE
_tic ()
DESCRIPTION
The `_tic' function resets the internal CPU timer. The
`_toc' may be used to read this timer. See the documentation
for the `_toc' function for more information.
EXAMPLE
SEE ALSO
_toc, times, tic, toc
--------------------------------------------------------------
tic
SYNOPSIS
Reset the interval timer
USAGE
void tic ()
DESCRIPTION
The `tic' function resets the internal interval timer. The
`toc' may be used to read the interval timer.
EXAMPLE
The tic/toc functions may be used to measure execution times. For
example, at the `slsh' prompt, they may be used to measure the speed
of a loop:
slsh> tic; loop (500000); toc;
0.06558
NOTES
On Unix, this timer makes use of the C library `gettimeofday'
function.
SEE ALSO
toc, times
--------------------------------------------------------------
_time
SYNOPSIS
Get the current calendar time in seconds
USAGE
Long_Type _time ()
DESCRIPTION
The `_time' function returns the number of elapsed seconds since
00:00:00 UTC, January 1, 1970. A number of functions (`ctime',
`gmtime', `localtime', etc.) are able to convert such a
value to other representations.
SEE ALSO
ctime, time, localtime, gmtime
--------------------------------------------------------------
time
SYNOPSIS
Return the current date and time as a string
USAGE
String_Type time ()
DESCRIPTION
This function returns the current time as a string of the form:
Sun Apr 21 13:34:17 1996
SEE ALSO
strftime, ctime, message, substr
--------------------------------------------------------------
times
SYNOPSIS
Get process times
USAGE
Struct_Type times ()
DESCRIPTION
The `times' function returns a structure containing the
following fields:
tms_utime (user time)
tms_stime (system time)
tms_cutime (user time of child processes)
tms_cstime (system time of child processes)
NOTES
Not all systems support this function.
SEE ALSO
_tic, _toc, _time
--------------------------------------------------------------
_toc
SYNOPSIS
Get the elapsed CPU time for the current process
USAGE
Double_Type _toc ()
DESCRIPTION
The `_toc' function returns the elapsed CPU time in seconds since
the last call to `_tic'. The CPU time is the amount of time the
CPU spent running the code of the current process.
EXAMPLE
NOTES
This function may not be available on all systems.
The implementation of this function is based upon the `times'
system call. The precision of the clock is system dependent and may
not be very accurate for small time intervals. For this reason, the
tic/toc functions may be more useful for small time-intervals.
SEE ALSO
_tic, _tic, _toc, times, _time
--------------------------------------------------------------
toc
SYNOPSIS
Read the interval timer
USAGE
Double_Type toc ()
DESCRIPTION
The `toc' function returns the elapsed time in seconds since
the last call to `tic'. See the documentation for the
`tic' function for more information.
SEE ALSO
tic, _tic, _toc, times, _time
--------------------------------------------------------------
atof
SYNOPSIS
Convert a string to a double precision number
USAGE
Double_Type atof (String_Type s)
DESCRIPTION
This function converts a string `s' to a double precision value
and returns the result. It performs no error checking on the format
of the string. The function `_slang_guess_type' may be used to
check the syntax of the string.
EXAMPLE
define error_checked_atof (s)
{
if (__is_datatype_numeric (_slang_guess_type (s)))
return atof (s);
throw InvalidParmError, "$s is not a double"$;
}
SEE ALSO
typecast, double, _slang_guess_type
--------------------------------------------------------------
atoi
SYNOPSIS
Convert a string to an integer
USAGE
Int_Type atoi (String_Type str)
DESCRIPTION
The `atoi' function converts a string to an `Int_Type'
using the standard C library function of the corresponding name.
NOTES
This function performs no syntax checking upon its argument.
SEE ALSO
integer, atol, atoll, atof, sscanf
--------------------------------------------------------------
atol
SYNOPSIS
Convert a string to an long integer
USAGE
Long_Type atol (String_Type str)
DESCRIPTION
The `atol' function converts a string to a `Long_Type'
using the standard C library function of the corresponding name.
NOTES
This function performs no syntax checking upon its argument.
SEE ALSO
integer, atoi, atoll, atof, sscanf
--------------------------------------------------------------
atoll
SYNOPSIS
Convert a string to a long long
USAGE
LLong_Type atoll (String_Type str)
DESCRIPTION
The `atoll' function converts a string to a `LLong_Type'
using the standard C library function of the corresponding name.
NOTES
This function performs no syntax checking upon its argument. Not
all platforms provide support for the long long data type.
SEE ALSO
integer, atoi, atol, atof, sscanf
--------------------------------------------------------------
char
SYNOPSIS
Convert a character code to a string
USAGE
String_Type char (Integer_Type c)
DESCRIPTION
The `char' function converts an integer character code (ascii)
value `c' to a string of unit character length such that the
first character of the string is `c'. For example,
`char('a')' returns the string `"a"'.
If UTF-8 mode is in effect (`_slang_utf8_ok' is non-zero), the
resulting single character may be represented by several bytes.
If the character code `c' is less than 0, then byte-semantics
will be used with the resulting string consisting of a single byte
whose value is that of `-c&0xFF'.
NOTES
A better name should have been chosen for this function.
SEE ALSO
integer, string, typedef, sprintf
--------------------------------------------------------------
define_case
SYNOPSIS
Define upper-lower case conversion
USAGE
define_case (Integer_Type ch_up, Integer_Type ch_low)
DESCRIPTION
This function defines an upper and lowercase relationship between two
characters specified by the arguments. This relationship is used by
routines which perform uppercase and lowercase conversions.
The first integer `ch_up' is the ascii value of the uppercase character
and the second parameter `ch_low' is the ascii value of its
lowercase counterpart.
NOTES
This function has no effect in UTF-8 mode.
SEE ALSO
strlow, strup
--------------------------------------------------------------
double
SYNOPSIS
Convert an object to double precision
USAGE
Double_Type double (x)
DESCRIPTION
The `double' function typecasts an object `x' to double
precision. For example, if `x' is an array of integers, an
array of double types will be returned. If an object cannot be
converted to `Double_Type', a type-mismatch error will result.
NOTES
The `double' function is equivalent to the typecast operation
typecast (x, Double_Type)
To convert a string to a double precision number, use the `atof'
function.
SEE ALSO
typecast, atof, int
--------------------------------------------------------------
int
SYNOPSIS
Typecast an object to an integer
USAGE
Int_Type int (s)
DESCRIPTION
This function performs a typecast of an object `s' to
an object of Integer_Type. If `s' is a string, it returns
returns the ascii value of the first bytes of the string
`s'. If `s' is Double_Type, `int' truncates the
number to an integer and returns it.
EXAMPLE
`int' can be used to convert single byte strings to
integers. As an example, the intrinsic function `isdigit' may
be defined as
define isdigit (s)
{
if ((int (s) >= '0') and (int (s) <= '9')) return 1;
return 0;
}
NOTES
This function is equivalent to `typecast (s, Integer_Type)';
SEE ALSO
typecast, double, integer, char, isdigit
--------------------------------------------------------------
integer
SYNOPSIS
Convert a string to an integer
USAGE
Integer_Type integer (String_Type s)
DESCRIPTION
The `integer' function converts a string representation of an
integer back to an integer. If the string does not form a valid
integer, a SyntaxError will be thrown.
EXAMPLE
`integer ("1234")' returns the integer value `1234'.
NOTES
This function operates only on strings and is not the same as the
more general `typecast' operator.
SEE ALSO
typecast, _slang_guess_type, string, sprintf, char
--------------------------------------------------------------
isdigit
SYNOPSIS
Tests for a decimal digit character
USAGE
Integer_Type isdigit (s)
DESCRIPTION
This function returns a non-zero value if the character represented
by `s' is a digit; otherwise, it returns zero. If `s' is
a string, the first character of `s' will be used for the test.
EXAMPLE
A simple, user defined implementation of `isdigit' is
define isdigit (x)
{
return ((x <= '9') and (x >= '0'));
}
However, the intrinsic function `isdigit' executes many times faster
than the representation defined above, and works properly when
`x' is a Unicode character.
SEE ALSO
int, integer
--------------------------------------------------------------
_slang_guess_type
SYNOPSIS
Guess the data type that a string represents
USAGE
DataType_Type _slang_guess_type (String_Type s)
DESCRIPTION
This function tries to determine whether its argument `s'
represents an integer (short, int, long), floating point (float,
double), or a complex number. If it appears to be none of these,
then a string is assumed. It returns one of the following values
depending on the format of the string `s':
Short_Type : short integer (e.g., "2h")
UShort_Type : unsigned short integer (e.g., "2hu")
Integer_Type : integer (e.g., "2")
UInteger_Type : unsigned integer (e.g., "2")
Long_Type : long integer (e.g., "2l")
ULong_Type : unsigned long integer (e.g., "2l")
Float_Type : float (e.g., "2.0f")
Double_Type : double (e.g., "2.0")
Complex_Type : imaginary (e.g., "2i")
String_Type : Anything else. (e.g., "2foo")
For example, `_slang_guess_type("1e2")' returns
Double_Type but `_slang_guess_type("e12")' returns
String_Type.
SEE ALSO
integer, string, double, atof, __is_datatype_numeric
--------------------------------------------------------------
string
SYNOPSIS
Convert an object to a string representation.
USAGE
String_Type string (obj)
DESCRIPTION
The `string' function may be used to convert an object
`obj' of any type to its string representation.
For example, `string(12.34)' returns `"12.34"'.
EXAMPLE
define print_anything (anything)
{
message (string (anything));
}
NOTES
This function is _not_ the same as typecasting to a String_Type
using the `typecast' function.
SEE ALSO
typecast, sprintf, integer, char
--------------------------------------------------------------
tolower
SYNOPSIS
Convert a character to lowercase.
USAGE
Integer_Type lower (Integer_Type ch)
DESCRIPTION
This function takes an integer `ch' and returns its lowercase
equivalent.
SEE ALSO
toupper, strup, strlow, int, char, define_case
--------------------------------------------------------------
toupper
SYNOPSIS
Convert a character to uppercase.
USAGE
Integer_Type toupper (Integer_Type ch)
DESCRIPTION
This function takes an integer `ch' and returns its uppercase
equivalent.
SEE ALSO
tolower, strup, strlow, int, char, define_case
--------------------------------------------------------------
typecast
SYNOPSIS
Convert an object from one data type to another.
USAGE
typecast (x, new_type)
DESCRIPTION
The `typecast' function performs a generic typecast operation on
`x' to convert it to `new_type'. If `x' represents an
array, the function will attempt to convert all elements of `x'
to `new_type'. Not all objects can be converted and a
type-mismatch error will result upon failure.
EXAMPLE
define to_complex (x)
{
return typecast (x, Complex_Type);
}
defines a function that converts its argument, `x' to a complex
number.
SEE ALSO
int, double, typeof
--------------------------------------------------------------
_typeof
SYNOPSIS
Get the data type of an object
USAGE
DataType_Type _typeof (x)
DESCRIPTION
This function is similar to the `typeof' function except in the
case of arrays. If the object `x' is an array, then the data
type of the array will be returned. otherwise `_typeof' returns
the data type of `x'.
EXAMPLE
if (Integer_Type == _typeof (x))
message ("x is an integer or an integer array");
SEE ALSO
typeof, array_info, _slang_guess_type, typecast
--------------------------------------------------------------
typeof
SYNOPSIS
Get the data type of an object
USAGE
DataType_Type typeof (x)
DESCRIPTION
This function returns the data type of `x'.
EXAMPLE
if (Integer_Type == typeof (x)) message ("x is an integer");
SEE ALSO
_typeof, is_struct_type, array_info, _slang_guess_type, typecast
--------------------------------------------------------------
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