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// Functor implementations -*- C++ -*-
// Copyright (C) 2001, 2002, 2004, 2005 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING. If not, write to the Free
// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
// USA.
// As a special exception, you may use this file as part of a free software
// library without restriction. Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License. This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.
/*
*
* Copyright (c) 1994
* Hewlett-Packard Company
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Hewlett-Packard Company makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*
*
* Copyright (c) 1996-1998
* Silicon Graphics Computer Systems, Inc.
*
* Permission to use, copy, modify, distribute and sell this software
* and its documentation for any purpose is hereby granted without fee,
* provided that the above copyright notice appear in all copies and
* that both that copyright notice and this permission notice appear
* in supporting documentation. Silicon Graphics makes no
* representations about the suitability of this software for any
* purpose. It is provided "as is" without express or implied warranty.
*/
/** @file stl_function.h
* This is an internal header file, included by other library headers.
* You should not attempt to use it directly.
*/
#ifndef _FUNCTION_H
#define _FUNCTION_H 1
_GLIBCXX_BEGIN_NAMESPACE(std)
// 20.3.1 base classes
/** @defgroup s20_3_1_base Functor Base Classes
* Function objects, or @e functors, are objects with an @c operator()
* defined and accessible. They can be passed as arguments to algorithm
* templates and used in place of a function pointer. Not only is the
* resulting expressiveness of the library increased, but the generated
* code can be more efficient than what you might write by hand. When we
* refer to "functors," then, generally we include function pointers in
* the description as well.
*
* Often, functors are only created as temporaries passed to algorithm
* calls, rather than being created as named variables.
*
* Two examples taken from the standard itself follow. To perform a
* by-element addition of two vectors @c a and @c b containing @c double,
* and put the result in @c a, use
* \code
* transform (a.begin(), a.end(), b.begin(), a.begin(), plus<double>());
* \endcode
* To negate every element in @c a, use
* \code
* transform(a.begin(), a.end(), a.begin(), negate<double>());
* \endcode
* The addition and negation functions will be inlined directly.
*
* The standard functors are derived from structs named @c unary_function
* and @c binary_function. These two classes contain nothing but typedefs,
* to aid in generic (template) programming. If you write your own
* functors, you might consider doing the same.
*
* @{
*/
/**
* This is one of the @link s20_3_1_base functor base classes@endlink.
*/
template <class _Arg, class _Result>
struct unary_function
{
typedef _Arg argument_type; ///< @c argument_type is the type of the
/// argument (no surprises here)
typedef _Result result_type; ///< @c result_type is the return type
};
/**
* This is one of the @link s20_3_1_base functor base classes@endlink.
*/
template <class _Arg1, class _Arg2, class _Result>
struct binary_function
{
typedef _Arg1 first_argument_type; ///< the type of the first argument
/// (no surprises here)
typedef _Arg2 second_argument_type; ///< the type of the second argument
typedef _Result result_type; ///< type of the return type
};
/** @} */
// 20.3.2 arithmetic
/** @defgroup s20_3_2_arithmetic Arithmetic Classes
* Because basic math often needs to be done during an algorithm, the library
* provides functors for those operations. See the documentation for
* @link s20_3_1_base the base classes@endlink for examples of their use.
*
* @{
*/
/// One of the @link s20_3_2_arithmetic math functors@endlink.
template <class _Tp>
struct plus : public binary_function<_Tp, _Tp, _Tp>
{
_Tp
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x + __y; }
};
/// One of the @link s20_3_2_arithmetic math functors@endlink.
template <class _Tp>
struct minus : public binary_function<_Tp, _Tp, _Tp>
{
_Tp
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x - __y; }
};
/// One of the @link s20_3_2_arithmetic math functors@endlink.
template <class _Tp>
struct multiplies : public binary_function<_Tp, _Tp, _Tp>
{
_Tp
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x * __y; }
};
/// One of the @link s20_3_2_arithmetic math functors@endlink.
template <class _Tp>
struct divides : public binary_function<_Tp, _Tp, _Tp>
{
_Tp
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x / __y; }
};
/// One of the @link s20_3_2_arithmetic math functors@endlink.
template <class _Tp>
struct modulus : public binary_function<_Tp, _Tp, _Tp>
{
_Tp
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x % __y; }
};
/// One of the @link s20_3_2_arithmetic math functors@endlink.
template <class _Tp>
struct negate : public unary_function<_Tp, _Tp>
{
_Tp
operator()(const _Tp& __x) const
{ return -__x; }
};
/** @} */
// 20.3.3 comparisons
/** @defgroup s20_3_3_comparisons Comparison Classes
* The library provides six wrapper functors for all the basic comparisons
* in C++, like @c <.
*
* @{
*/
/// One of the @link s20_3_3_comparisons comparison functors@endlink.
template <class _Tp>
struct equal_to : public binary_function<_Tp, _Tp, bool>
{
bool
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x == __y; }
};
/// One of the @link s20_3_3_comparisons comparison functors@endlink.
template <class _Tp>
struct not_equal_to : public binary_function<_Tp, _Tp, bool>
{
bool
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x != __y; }
};
/// One of the @link s20_3_3_comparisons comparison functors@endlink.
template <class _Tp>
struct greater : public binary_function<_Tp, _Tp, bool>
{
bool
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x > __y; }
};
/// One of the @link s20_3_3_comparisons comparison functors@endlink.
template <class _Tp>
struct less : public binary_function<_Tp, _Tp, bool>
{
bool
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x < __y; }
};
/// One of the @link s20_3_3_comparisons comparison functors@endlink.
template <class _Tp>
struct greater_equal : public binary_function<_Tp, _Tp, bool>
{
bool
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x >= __y; }
};
/// One of the @link s20_3_3_comparisons comparison functors@endlink.
template <class _Tp>
struct less_equal : public binary_function<_Tp, _Tp, bool>
{
bool
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x <= __y; }
};
/** @} */
// 20.3.4 logical operations
/** @defgroup s20_3_4_logical Boolean Operations Classes
* Here are wrapper functors for Boolean operations: @c &&, @c ||, and @c !.
*
* @{
*/
/// One of the @link s20_3_4_logical Boolean operations functors@endlink.
template <class _Tp>
struct logical_and : public binary_function<_Tp, _Tp, bool>
{
bool
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x && __y; }
};
/// One of the @link s20_3_4_logical Boolean operations functors@endlink.
template <class _Tp>
struct logical_or : public binary_function<_Tp, _Tp, bool>
{
bool
operator()(const _Tp& __x, const _Tp& __y) const
{ return __x || __y; }
};
/// One of the @link s20_3_4_logical Boolean operations functors@endlink.
template <class _Tp>
struct logical_not : public unary_function<_Tp, bool>
{
bool
operator()(const _Tp& __x) const
{ return !__x; }
};
/** @} */
// 20.3.5 negators
/** @defgroup s20_3_5_negators Negators
* The functions @c not1 and @c not2 each take a predicate functor
* and return an instance of @c unary_negate or
* @c binary_negate, respectively. These classes are functors whose
* @c operator() performs the stored predicate function and then returns
* the negation of the result.
*
* For example, given a vector of integers and a trivial predicate,
* \code
* struct IntGreaterThanThree
* : public std::unary_function<int, bool>
* {
* bool operator() (int x) { return x > 3; }
* };
*
* std::find_if (v.begin(), v.end(), not1(IntGreaterThanThree()));
* \endcode
* The call to @c find_if will locate the first index (i) of @c v for which
* "!(v[i] > 3)" is true.
*
* The not1/unary_negate combination works on predicates taking a single
* argument. The not2/binary_negate combination works on predicates which
* take two arguments.
*
* @{
*/
/// One of the @link s20_3_5_negators negation functors@endlink.
template <class _Predicate>
class unary_negate
: public unary_function<typename _Predicate::argument_type, bool>
{
protected:
_Predicate _M_pred;
public:
explicit
unary_negate(const _Predicate& __x) : _M_pred(__x) {}
bool
operator()(const typename _Predicate::argument_type& __x) const
{ return !_M_pred(__x); }
};
/// One of the @link s20_3_5_negators negation functors@endlink.
template <class _Predicate>
inline unary_negate<_Predicate>
not1(const _Predicate& __pred)
{ return unary_negate<_Predicate>(__pred); }
/// One of the @link s20_3_5_negators negation functors@endlink.
template <class _Predicate>
class binary_negate
: public binary_function<typename _Predicate::first_argument_type,
typename _Predicate::second_argument_type,
bool>
{
protected:
_Predicate _M_pred;
public:
explicit
binary_negate(const _Predicate& __x)
: _M_pred(__x) { }
bool
operator()(const typename _Predicate::first_argument_type& __x,
const typename _Predicate::second_argument_type& __y) const
{ return !_M_pred(__x, __y); }
};
/// One of the @link s20_3_5_negators negation functors@endlink.
template <class _Predicate>
inline binary_negate<_Predicate>
not2(const _Predicate& __pred)
{ return binary_negate<_Predicate>(__pred); }
/** @} */
// 20.3.6 binders
/** @defgroup s20_3_6_binder Binder Classes
* Binders turn functions/functors with two arguments into functors with
* a single argument, storing an argument to be applied later. For
* example, a variable @c B of type @c binder1st is constructed from a
* functor @c f and an argument @c x. Later, B's @c operator() is called
* with a single argument @c y. The return value is the value of @c f(x,y).
* @c B can be "called" with various arguments (y1, y2, ...) and will in
* turn call @c f(x,y1), @c f(x,y2), ...
*
* The function @c bind1st is provided to save some typing. It takes the
* function and an argument as parameters, and returns an instance of
* @c binder1st.
*
* The type @c binder2nd and its creator function @c bind2nd do the same
* thing, but the stored argument is passed as the second parameter instead
* of the first, e.g., @c bind2nd(std::minus<float>,1.3) will create a
* functor whose @c operator() accepts a floating-point number, subtracts
* 1.3 from it, and returns the result. (If @c bind1st had been used,
* the functor would perform "1.3 - x" instead.
*
* Creator-wrapper functions like @c bind1st are intended to be used in
* calling algorithms. Their return values will be temporary objects.
* (The goal is to not require you to type names like
* @c std::binder1st<std::plus<int>> for declaring a variable to hold the
* return value from @c bind1st(std::plus<int>,5).
*
* These become more useful when combined with the composition functions.
*
* @{
*/
/// One of the @link s20_3_6_binder binder functors@endlink.
template <class _Operation>
class binder1st
: public unary_function<typename _Operation::second_argument_type,
typename _Operation::result_type>
{
protected:
_Operation op;
typename _Operation::first_argument_type value;
public:
binder1st(const _Operation& __x,
const typename _Operation::first_argument_type& __y)
: op(__x), value(__y) {}
typename _Operation::result_type
operator()(const typename _Operation::second_argument_type& __x) const
{ return op(value, __x); }
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 109. Missing binders for non-const sequence elements
typename _Operation::result_type
operator()(typename _Operation::second_argument_type& __x) const
{ return op(value, __x); }
};
/// One of the @link s20_3_6_binder binder functors@endlink.
template <class _Operation, class _Tp>
inline binder1st<_Operation>
bind1st(const _Operation& __fn, const _Tp& __x)
{
typedef typename _Operation::first_argument_type _Arg1_type;
return binder1st<_Operation>(__fn, _Arg1_type(__x));
}
/// One of the @link s20_3_6_binder binder functors@endlink.
template <class _Operation>
class binder2nd
: public unary_function<typename _Operation::first_argument_type,
typename _Operation::result_type>
{
protected:
_Operation op;
typename _Operation::second_argument_type value;
public:
binder2nd(const _Operation& __x,
const typename _Operation::second_argument_type& __y)
: op(__x), value(__y) {}
typename _Operation::result_type
operator()(const typename _Operation::first_argument_type& __x) const
{ return op(__x, value); }
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 109. Missing binders for non-const sequence elements
typename _Operation::result_type
operator()(typename _Operation::first_argument_type& __x) const
{ return op(__x, value); }
};
/// One of the @link s20_3_6_binder binder functors@endlink.
template <class _Operation, class _Tp>
inline binder2nd<_Operation>
bind2nd(const _Operation& __fn, const _Tp& __x)
{
typedef typename _Operation::second_argument_type _Arg2_type;
return binder2nd<_Operation>(__fn, _Arg2_type(__x));
}
/** @} */
// 20.3.7 adaptors pointers functions
/** @defgroup s20_3_7_adaptors Adaptors for pointers to functions
* The advantage of function objects over pointers to functions is that
* the objects in the standard library declare nested typedefs describing
* their argument and result types with uniform names (e.g., @c result_type
* from the base classes @c unary_function and @c binary_function).
* Sometimes those typedefs are required, not just optional.
*
* Adaptors are provided to turn pointers to unary (single-argument) and
* binary (double-argument) functions into function objects. The
* long-winded functor @c pointer_to_unary_function is constructed with a
* function pointer @c f, and its @c operator() called with argument @c x
* returns @c f(x). The functor @c pointer_to_binary_function does the same
* thing, but with a double-argument @c f and @c operator().
*
* The function @c ptr_fun takes a pointer-to-function @c f and constructs
* an instance of the appropriate functor.
*
* @{
*/
/// One of the @link s20_3_7_adaptors adaptors for function pointers@endlink.
template <class _Arg, class _Result>
class pointer_to_unary_function : public unary_function<_Arg, _Result>
{
protected:
_Result (*_M_ptr)(_Arg);
public:
pointer_to_unary_function() {}
explicit
pointer_to_unary_function(_Result (*__x)(_Arg))
: _M_ptr(__x) {}
_Result
operator()(_Arg __x) const
{ return _M_ptr(__x); }
};
/// One of the @link s20_3_7_adaptors adaptors for function pointers@endlink.
template <class _Arg, class _Result>
inline pointer_to_unary_function<_Arg, _Result>
ptr_fun(_Result (*__x)(_Arg))
{ return pointer_to_unary_function<_Arg, _Result>(__x); }
/// One of the @link s20_3_7_adaptors adaptors for function pointers@endlink.
template <class _Arg1, class _Arg2, class _Result>
class pointer_to_binary_function
: public binary_function<_Arg1, _Arg2, _Result>
{
protected:
_Result (*_M_ptr)(_Arg1, _Arg2);
public:
pointer_to_binary_function() {}
explicit
pointer_to_binary_function(_Result (*__x)(_Arg1, _Arg2))
: _M_ptr(__x) {}
_Result
operator()(_Arg1 __x, _Arg2 __y) const
{ return _M_ptr(__x, __y); }
};
/// One of the @link s20_3_7_adaptors adaptors for function pointers@endlink.
template <class _Arg1, class _Arg2, class _Result>
inline pointer_to_binary_function<_Arg1, _Arg2, _Result>
ptr_fun(_Result (*__x)(_Arg1, _Arg2))
{ return pointer_to_binary_function<_Arg1, _Arg2, _Result>(__x); }
/** @} */
template <class _Tp>
struct _Identity : public unary_function<_Tp,_Tp>
{
_Tp&
operator()(_Tp& __x) const
{ return __x; }
const _Tp&
operator()(const _Tp& __x) const
{ return __x; }
};
template <class _Pair>
struct _Select1st : public unary_function<_Pair,
typename _Pair::first_type>
{
typename _Pair::first_type&
operator()(_Pair& __x) const
{ return __x.first; }
const typename _Pair::first_type&
operator()(const _Pair& __x) const
{ return __x.first; }
};
template <class _Pair>
struct _Select2nd : public unary_function<_Pair,
typename _Pair::second_type>
{
typename _Pair::second_type&
operator()(_Pair& __x) const
{ return __x.second; }
const typename _Pair::second_type&
operator()(const _Pair& __x) const
{ return __x.second; }
};
// 20.3.8 adaptors pointers members
/** @defgroup s20_3_8_memadaptors Adaptors for pointers to members
* There are a total of 8 = 2^3 function objects in this family.
* (1) Member functions taking no arguments vs member functions taking
* one argument.
* (2) Call through pointer vs call through reference.
* (3) Const vs non-const member function.
*
* All of this complexity is in the function objects themselves. You can
* ignore it by using the helper function mem_fun and mem_fun_ref,
* which create whichever type of adaptor is appropriate.
*
* @{
*/
/// One of the @link s20_3_8_memadaptors adaptors for member pointers@endlink.
template <class _Ret, class _Tp>
class mem_fun_t : public unary_function<_Tp*, _Ret>
{
public:
explicit
mem_fun_t(_Ret (_Tp::*__pf)())
: _M_f(__pf) {}
_Ret
operator()(_Tp* __p) const
{ return (__p->*_M_f)(); }
private:
_Ret (_Tp::*_M_f)();
};
/// One of the @link s20_3_8_memadaptors adaptors for member pointers@endlink.
template <class _Ret, class _Tp>
class const_mem_fun_t : public unary_function<const _Tp*, _Ret>
{
public:
explicit
const_mem_fun_t(_Ret (_Tp::*__pf)() const)
: _M_f(__pf) {}
_Ret
operator()(const _Tp* __p) const
{ return (__p->*_M_f)(); }
private:
_Ret (_Tp::*_M_f)() const;
};
/// One of the @link s20_3_8_memadaptors adaptors for member pointers@endlink.
template <class _Ret, class _Tp>
class mem_fun_ref_t : public unary_function<_Tp, _Ret>
{
public:
explicit
mem_fun_ref_t(_Ret (_Tp::*__pf)())
: _M_f(__pf) {}
_Ret
operator()(_Tp& __r) const
{ return (__r.*_M_f)(); }
private:
_Ret (_Tp::*_M_f)();
};
/// One of the @link s20_3_8_memadaptors adaptors for member pointers@endlink.
template <class _Ret, class _Tp>
class const_mem_fun_ref_t : public unary_function<_Tp, _Ret>
{
public:
explicit
const_mem_fun_ref_t(_Ret (_Tp::*__pf)() const)
: _M_f(__pf) {}
_Ret
operator()(const _Tp& __r) const
{ return (__r.*_M_f)(); }
private:
_Ret (_Tp::*_M_f)() const;
};
/// One of the @link s20_3_8_memadaptors adaptors for member pointers@endlink.
template <class _Ret, class _Tp, class _Arg>
class mem_fun1_t : public binary_function<_Tp*, _Arg, _Ret>
{
public:
explicit
mem_fun1_t(_Ret (_Tp::*__pf)(_Arg))
: _M_f(__pf) {}
_Ret
operator()(_Tp* __p, _Arg __x) const
{ return (__p->*_M_f)(__x); }
private:
_Ret (_Tp::*_M_f)(_Arg);
};
/// One of the @link s20_3_8_memadaptors adaptors for member pointers@endlink.
template <class _Ret, class _Tp, class _Arg>
class const_mem_fun1_t : public binary_function<const _Tp*, _Arg, _Ret>
{
public:
explicit
const_mem_fun1_t(_Ret (_Tp::*__pf)(_Arg) const)
: _M_f(__pf) {}
_Ret
operator()(const _Tp* __p, _Arg __x) const
{ return (__p->*_M_f)(__x); }
private:
_Ret (_Tp::*_M_f)(_Arg) const;
};
/// One of the @link s20_3_8_memadaptors adaptors for member pointers@endlink.
template <class _Ret, class _Tp, class _Arg>
class mem_fun1_ref_t : public binary_function<_Tp, _Arg, _Ret>
{
public:
explicit
mem_fun1_ref_t(_Ret (_Tp::*__pf)(_Arg))
: _M_f(__pf) {}
_Ret
operator()(_Tp& __r, _Arg __x) const
{ return (__r.*_M_f)(__x); }
private:
_Ret (_Tp::*_M_f)(_Arg);
};
/// One of the @link s20_3_8_memadaptors adaptors for member pointers@endlink.
template <class _Ret, class _Tp, class _Arg>
class const_mem_fun1_ref_t : public binary_function<_Tp, _Arg, _Ret>
{
public:
explicit
const_mem_fun1_ref_t(_Ret (_Tp::*__pf)(_Arg) const)
: _M_f(__pf) {}
_Ret
operator()(const _Tp& __r, _Arg __x) const
{ return (__r.*_M_f)(__x); }
private:
_Ret (_Tp::*_M_f)(_Arg) const;
};
// Mem_fun adaptor helper functions. There are only two:
// mem_fun and mem_fun_ref.
template <class _Ret, class _Tp>
inline mem_fun_t<_Ret, _Tp>
mem_fun(_Ret (_Tp::*__f)())
{ return mem_fun_t<_Ret, _Tp>(__f); }
template <class _Ret, class _Tp>
inline const_mem_fun_t<_Ret, _Tp>
mem_fun(_Ret (_Tp::*__f)() const)
{ return const_mem_fun_t<_Ret, _Tp>(__f); }
template <class _Ret, class _Tp>
inline mem_fun_ref_t<_Ret, _Tp>
mem_fun_ref(_Ret (_Tp::*__f)())
{ return mem_fun_ref_t<_Ret, _Tp>(__f); }
template <class _Ret, class _Tp>
inline const_mem_fun_ref_t<_Ret, _Tp>
mem_fun_ref(_Ret (_Tp::*__f)() const)
{ return const_mem_fun_ref_t<_Ret, _Tp>(__f); }
template <class _Ret, class _Tp, class _Arg>
inline mem_fun1_t<_Ret, _Tp, _Arg>
mem_fun(_Ret (_Tp::*__f)(_Arg))
{ return mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
template <class _Ret, class _Tp, class _Arg>
inline const_mem_fun1_t<_Ret, _Tp, _Arg>
mem_fun(_Ret (_Tp::*__f)(_Arg) const)
{ return const_mem_fun1_t<_Ret, _Tp, _Arg>(__f); }
template <class _Ret, class _Tp, class _Arg>
inline mem_fun1_ref_t<_Ret, _Tp, _Arg>
mem_fun_ref(_Ret (_Tp::*__f)(_Arg))
{ return mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
template <class _Ret, class _Tp, class _Arg>
inline const_mem_fun1_ref_t<_Ret, _Tp, _Arg>
mem_fun_ref(_Ret (_Tp::*__f)(_Arg) const)
{ return const_mem_fun1_ref_t<_Ret, _Tp, _Arg>(__f); }
/** @} */
_GLIBCXX_END_NAMESPACE
#endif /* _FUNCTION_H */
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