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 // Suppress deprecated warning for this file.
60 #pragma GCC diagnostic push
61 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
62 
63 namespace std _GLIBCXX_VISIBILITY(default)
64 {
65 _GLIBCXX_BEGIN_NAMESPACE_VERSION
66 
67  // 20.3.6 binders
68  /** @defgroup binders Binder Classes
69  * @ingroup functors
70  *
71  * Binders turn functions/functors with two arguments into functors
72  * with a single argument, storing an argument to be applied later.
73  * For example, a variable @c B of type @c binder1st is constructed
74  * from a functor @c f and an argument @c x. Later, B's @c
75  * operator() is called with a single argument @c y. The return
76  * value is the value of @c f(x,y). @c B can be @a called with
77  * various arguments (y1, y2, ...) and will in turn call @c
78  * f(x,y1), @c f(x,y2), ...
79  *
80  * The function @c bind1st is provided to save some typing. It takes the
81  * function and an argument as parameters, and returns an instance of
82  * @c binder1st.
83  *
84  * The type @c binder2nd and its creator function @c bind2nd do the same
85  * thing, but the stored argument is passed as the second parameter instead
86  * of the first, e.g., @c bind2nd(std::minus<float>(),1.3) will create a
87  * functor whose @c operator() accepts a floating-point number, subtracts
88  * 1.3 from it, and returns the result. (If @c bind1st had been used,
89  * the functor would perform <em>1.3 - x</em> instead.
90  *
91  * Creator-wrapper functions like @c bind1st are intended to be used in
92  * calling algorithms. Their return values will be temporary objects.
93  * (The goal is to not require you to type names like
94  * @c std::binder1st<std::plus<int>> for declaring a variable to hold the
95  * return value from @c bind1st(std::plus<int>(),5).
96  *
97  * These become more useful when combined with the composition functions.
98  *
99  * These functions are deprecated in C++11 and can be replaced by
100  * @c std::bind (or @c std::tr1::bind) which is more powerful and flexible,
101  * supporting functions with any number of arguments. Uses of @c bind1st
102  * can be replaced by @c std::bind(f, x, std::placeholders::_1) and
103  * @c bind2nd by @c std::bind(f, std::placeholders::_1, x).
104  * @{
105  */
106  /// One of the @link binders binder functors@endlink.
107  template<typename _Operation>
108  class binder1st
109  : public unary_function<typename _Operation::second_argument_type,
110  typename _Operation::result_type>
111  {
112  protected:
113  _Operation op;
114  typename _Operation::first_argument_type value;
115 
116  public:
117  binder1st(const _Operation& __x,
118  const typename _Operation::first_argument_type& __y)
119  : op(__x), value(__y) { }
120 
121  typename _Operation::result_type
122  operator()(const typename _Operation::second_argument_type& __x) const
123  { return op(value, __x); }
124 
125  // _GLIBCXX_RESOLVE_LIB_DEFECTS
126  // 109. Missing binders for non-const sequence elements
127  typename _Operation::result_type
128  operator()(typename _Operation::second_argument_type& __x) const
129  { return op(value, __x); }
130  } _GLIBCXX_DEPRECATED;
131 
132  /// One of the @link binders binder functors@endlink.
133  template<typename _Operation, typename _Tp>
134  inline binder1st<_Operation>
135  bind1st(const _Operation& __fn, const _Tp& __x)
136  {
137  typedef typename _Operation::first_argument_type _Arg1_type;
138  return binder1st<_Operation>(__fn, _Arg1_type(__x));
139  }
140 
141  /// One of the @link binders binder functors@endlink.
142  template<typename _Operation>
143  class binder2nd
144  : public unary_function<typename _Operation::first_argument_type,
145  typename _Operation::result_type>
146  {
147  protected:
148  _Operation op;
149  typename _Operation::second_argument_type value;
150 
151  public:
152  binder2nd(const _Operation& __x,
153  const typename _Operation::second_argument_type& __y)
154  : op(__x), value(__y) { }
155 
156  typename _Operation::result_type
157  operator()(const typename _Operation::first_argument_type& __x) const
158  { return op(__x, value); }
159 
160  // _GLIBCXX_RESOLVE_LIB_DEFECTS
161  // 109. Missing binders for non-const sequence elements
162  typename _Operation::result_type
163  operator()(typename _Operation::first_argument_type& __x) const
164  { return op(__x, value); }
165  } _GLIBCXX_DEPRECATED;
166 
167  /// One of the @link binders binder functors@endlink.
168  template<typename _Operation, typename _Tp>
169  inline binder2nd<_Operation>
170  bind2nd(const _Operation& __fn, const _Tp& __x)
171  {
172  typedef typename _Operation::second_argument_type _Arg2_type;
173  return binder2nd<_Operation>(__fn, _Arg2_type(__x));
174  }
175  /** @} */
176 
177 _GLIBCXX_END_NAMESPACE_VERSION
178 } // namespace
179 
180 #pragma GCC diagnostic pop
181 
182 #endif /* _BACKWARD_BINDERS_H */
binder1st< _Operation > bind1st(const _Operation &__fn, const _Tp &__x)
One of the binder functors.
Definition: binders.h:135
One of the binder functors.
Definition: binders.h:108
binder2nd< _Operation > bind2nd(const _Operation &__fn, const _Tp &__x)
One of the binder functors.
Definition: binders.h:170
ISO C++ entities toplevel namespace is std.
One of the binder functors.
Definition: binders.h:143