libstdc++
binders.h
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50 
51 /** @file backward/binders.h
52  * This is an internal header file, included by other library headers.
53  * Do not attempt to use it directly. @headername{functional}
54  */
55 
56 #ifndef _BACKWARD_BINDERS_H
57 #define _BACKWARD_BINDERS_H 1
58 
59 namespace std _GLIBCXX_VISIBILITY(default)
60 {
61 _GLIBCXX_BEGIN_NAMESPACE_VERSION
62 
63  // 20.3.6 binders
64  /** @defgroup binders Binder Classes
65  * @ingroup functors
66  *
67  * Binders turn functions/functors with two arguments into functors
68  * with a single argument, storing an argument to be applied later.
69  * For example, a variable @c B of type @c binder1st is constructed
70  * from a functor @c f and an argument @c x. Later, B's @c
71  * operator() is called with a single argument @c y. The return
72  * value is the value of @c f(x,y). @c B can be @a called with
73  * various arguments (y1, y2, ...) and will in turn call @c
74  * f(x,y1), @c f(x,y2), ...
75  *
76  * The function @c bind1st is provided to save some typing. It takes the
77  * function and an argument as parameters, and returns an instance of
78  * @c binder1st.
79  *
80  * The type @c binder2nd and its creator function @c bind2nd do the same
81  * thing, but the stored argument is passed as the second parameter instead
82  * of the first, e.g., @c bind2nd(std::minus<float>(),1.3) will create a
83  * functor whose @c operator() accepts a floating-point number, subtracts
84  * 1.3 from it, and returns the result. (If @c bind1st had been used,
85  * the functor would perform <em>1.3 - x</em> instead.
86  *
87  * Creator-wrapper functions like @c bind1st are intended to be used in
88  * calling algorithms. Their return values will be temporary objects.
89  * (The goal is to not require you to type names like
90  * @c std::binder1st<std::plus<int>> for declaring a variable to hold the
91  * return value from @c bind1st(std::plus<int>(),5).
92  *
93  * These become more useful when combined with the composition functions.
94  *
95  * These functions are deprecated in C++11 and can be replaced by
96  * @c std::bind (or @c std::tr1::bind) which is more powerful and flexible,
97  * supporting functions with any number of arguments. Uses of @c bind1st
98  * can be replaced by @c std::bind(f, x, std::placeholders::_1) and
99  * @c bind2nd by @c std::bind(f, std::placeholders::_1, x).
100  * @{
101  */
102  /// One of the @link binders binder functors@endlink.
103  template<typename _Operation>
104  class binder1st
105  : public unary_function<typename _Operation::second_argument_type,
106  typename _Operation::result_type>
107  {
108  protected:
109  _Operation op;
110  typename _Operation::first_argument_type value;
111 
112  public:
113  binder1st(const _Operation& __x,
114  const typename _Operation::first_argument_type& __y)
115  : op(__x), value(__y) { }
116 
117  typename _Operation::result_type
118  operator()(const typename _Operation::second_argument_type& __x) const
119  { return op(value, __x); }
120 
121  // _GLIBCXX_RESOLVE_LIB_DEFECTS
122  // 109. Missing binders for non-const sequence elements
123  typename _Operation::result_type
124  operator()(typename _Operation::second_argument_type& __x) const
125  { return op(value, __x); }
126  } _GLIBCXX_DEPRECATED;
127 
128  /// One of the @link binders binder functors@endlink.
129  template<typename _Operation, typename _Tp>
130  inline binder1st<_Operation>
131  bind1st(const _Operation& __fn, const _Tp& __x)
132  {
133  typedef typename _Operation::first_argument_type _Arg1_type;
134  return binder1st<_Operation>(__fn, _Arg1_type(__x));
135  }
136 
137  /// One of the @link binders binder functors@endlink.
138  template<typename _Operation>
139  class binder2nd
140  : public unary_function<typename _Operation::first_argument_type,
141  typename _Operation::result_type>
142  {
143  protected:
144  _Operation op;
145  typename _Operation::second_argument_type value;
146 
147  public:
148  binder2nd(const _Operation& __x,
149  const typename _Operation::second_argument_type& __y)
150  : op(__x), value(__y) { }
151 
152  typename _Operation::result_type
153  operator()(const typename _Operation::first_argument_type& __x) const
154  { return op(__x, value); }
155 
156  // _GLIBCXX_RESOLVE_LIB_DEFECTS
157  // 109. Missing binders for non-const sequence elements
158  typename _Operation::result_type
159  operator()(typename _Operation::first_argument_type& __x) const
160  { return op(__x, value); }
161  } _GLIBCXX_DEPRECATED;
162 
163  /// One of the @link binders binder functors@endlink.
164  template<typename _Operation, typename _Tp>
165  inline binder2nd<_Operation>
166  bind2nd(const _Operation& __fn, const _Tp& __x)
167  {
168  typedef typename _Operation::second_argument_type _Arg2_type;
169  return binder2nd<_Operation>(__fn, _Arg2_type(__x));
170  }
171  /** @} */
172 
173 _GLIBCXX_END_NAMESPACE_VERSION
174 } // namespace
175 
176 #endif /* _BACKWARD_BINDERS_H */
One of the binder functors.
Definition: binders.h:139
binder2nd< _Operation > bind2nd(const _Operation &__fn, const _Tp &__x)
One of the binder functors.
Definition: binders.h:166
One of the binder functors.
Definition: binders.h:104
ISO C++ entities toplevel namespace is std.
binder1st< _Operation > bind1st(const _Operation &__fn, const _Tp &__x)
One of the binder functors.
Definition: binders.h:131