binders.h
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// Functor implementations -*- C++ -*-
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/** @file backward/binders.h
* This is an internal header file, included by other library headers.
* Do not attempt to use it directly. @headername{functional}
*/
#ifndef _BACKWARD_BINDERS_H
#define _BACKWARD_BINDERS_H 1
namespace std _GLIBCXX_VISIBILITY(default)
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION
// 20.3.6 binders
/** @defgroup binders Binder Classes
* @ingroup functors
*
* 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 @a 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 <em>1.3 - x</em> 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.
*
* These functions are deprecated in C++11 and can be replaced by
* @c std::bind (or @c std::tr1::bind) which is more powerful and flexible,
* supporting functions with any number of arguments. Uses of @c bind1st
* can be replaced by @c std::bind(f, x, std::placeholders::_1) and
* @c bind2nd by @c std::bind(f, std::placeholders::_1, x).
* @{
*/
/// One of the @link binders binder functors@endlink.
template<typename _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); }
} _GLIBCXX_DEPRECATED;
/// One of the @link binders binder functors@endlink.
template<typename _Operation, typename _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 binders binder functors@endlink.
template<typename _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); }
} _GLIBCXX_DEPRECATED;
/// One of the @link binders binder functors@endlink.
template<typename _Operation, typename _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));
}
/** @} */
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace
#endif /* _BACKWARD_BINDERS_H */
std::binder1st
One of the binder functors.
Definition: binders.h:104
std::bind1st
binder1st< _Operation > bind1st(const _Operation &__fn, const _Tp &__x)
One of the binder functors.
Definition: binders.h:131
std::binder2nd
One of the binder functors.
Definition: binders.h:139
std::bind2nd
binder2nd< _Operation > bind2nd(const _Operation &__fn, const _Tp &__x)
One of the binder functors.
Definition: binders.h:166
std::unary_function
Definition: stl_function.h:105