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overload.hpp
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1 // Range v3 library
3 //
4 // Copyright Eric Niebler 2013-present
5 //
6 // Use, modification and distribution is subject to the
7 // Boost Software License, Version 1.0. (See accompanying
8 // file LICENSE_1_0.txt or copy at
9 // http://www.boost.org/LICENSE_1_0.txt)
10 //
11 // Project home: https://github.com/ericniebler/range-v3
12 //
13 #ifndef RANGES_V3_FUNCTIONAL_OVERLOAD_HPP
14 #define RANGES_V3_FUNCTIONAL_OVERLOAD_HPP
15 
16 #include <meta/meta.hpp>
17 
18 #include <concepts/concepts.hpp>
19 
20 #include <range/v3/range_fwd.hpp>
21 
24 #include <range/v3/utility/static_const.hpp>
25 
26 #include <range/v3/detail/prologue.hpp>
27 
28 namespace ranges
29 {
33  namespace detail
34  {
35  struct _id
36  {
37  template<typename T>
38  using invoke = T;
39  };
40  struct _ref
41  {
42  template<typename T>
43  using invoke = T &;
44  };
45  struct _cref
46  {
47  template<typename T>
48  using invoke = T const &;
49  };
50  template<typename T>
51  struct _bind_front
52  {
53  template<typename... Args>
54  using invoke = invoke_result_t<T, Args...>;
55  };
56  } // namespace detail
58 
59  template<typename... Ts>
60  struct overloaded;
61 
62  template<>
63  struct overloaded<>
64  {
65  private:
66  template<typename...>
67  friend struct overloaded;
68  template<typename, typename...>
69  using _result_t = void;
70  };
71 
72  template<typename First, typename... Rest>
73  struct overloaded<First, Rest...>
74  {
75  private:
76  template<typename...>
77  friend struct overloaded;
78 
79  RANGES_NO_UNIQUE_ADDRESS
80  First first_;
81  RANGES_NO_UNIQUE_ADDRESS
82  overloaded<Rest...> second_;
83 
84  template<typename Qual>
85  using _result_first = detail::_bind_front<meta::invoke<Qual, First>>;
86  template<typename Qual>
87  struct _result_second
88  {
89  template<typename... Args>
90  using invoke = typename overloaded<Rest...>
91  ::template _result_t<Qual, Args...>;
92  };
93 
94  template<typename Qual, typename... Args>
95  using _result_t =
98  (bool) invocable<meta::invoke<Qual, First>, Args...>,
99  _result_first<Qual>,
100  _result_second<Qual>>,
101  Args...>;
102 
103  public:
104  overloaded() = default;
105  constexpr overloaded(First first, Rest... rest)
106  : first_(static_cast<First &&>(first))
107  , second_{static_cast<Rest &&>(rest)...}
108  {}
109 
110  template(typename... Args)(
111  requires invocable<First, Args...>)
112  constexpr _result_t<detail::_id, Args...> operator()(Args &&... args) &&
113  {
114  return invoke((First &&) first_, (Args &&) args...);
115  }
116  template(typename... Args)(
117  requires (!invocable<First, Args...>) AND
118  invocable<overloaded<Rest...>, Args...>)
119  constexpr _result_t<detail::_id, Args...> operator()(Args &&... args) &&
120  {
121  return invoke((overloaded<Rest...> &&) second_, (Args &&) args...);
122  }
123 
124  template(typename... Args)(
125  requires invocable<First &, Args...>)
126  constexpr _result_t<detail::_ref, Args...> operator()(Args &&... args) &
127  {
128  return invoke(first_, (Args &&) args...);
129  }
130  template(typename... Args)(
131  requires (!invocable<First &, Args...>) AND
132  invocable<overloaded<Rest...> &, Args...>)
133  constexpr _result_t<detail::_ref, Args...> operator()(Args &&... args) &
134  {
135  return invoke(second_, (Args &&) args...);
136  }
137 
138  template(typename... Args)(
139  requires invocable<First const &, Args...>)
140  constexpr _result_t<detail::_cref, Args...> operator()(Args &&... args) const &
141  {
142  return invoke(first_, (Args &&) args...);
143  }
144  template(typename... Args)(
145  requires (!invocable<First const &, Args...>) AND
146  invocable<overloaded<Rest...> const &, Args...>)
147  constexpr _result_t<detail::_cref, Args...> operator()(Args &&... args) const &
148  {
149  return invoke(second_, (Args &&) args...);
150  }
151  };
152 
153  struct overload_fn
154  {
155  template<typename Fn>
156  constexpr Fn operator()(Fn fn) const
157  {
158  return fn;
159  }
160  template<typename... Fns>
161  constexpr overloaded<Fns...> operator()(Fns... fns) const
162  {
163  return overloaded<Fns...>{static_cast<Fns &&>(fns)...};
164  }
165  };
166 
171 } // namespace ranges
172 
173 #include <range/v3/detail/epilogue.hpp>
174 
175 #endif
template(typename ActionFn, typename Rng)(concept(invocable_action_closure_)(ActionFn
\concept invocable_action_closure_
CPP_concept invocable
\concept invocable
Definition: concepts.hpp:48
RANGES_INLINE_VARIABLE(detail::to_container_fn< detail::from_range< std::vector >>, to_vector) template< template< typename... > class ContT > auto to(RANGES_HIDDEN_DETAIL(detail
For initializing a container of the specified type with the elements of an Range.
Definition: conversion.hpp:399
typename Fn::template invoke< Args... > invoke
Evaluate the invocable Fn with the arguments Args.
Definition: meta.hpp:541
front< Pair > first
Retrieve the first element of the pair Pair.
Definition: meta.hpp:2251
typename detail::_cond< If >::template invoke< Then, Else > conditional_t
Select one type or another depending on a compile-time Boolean.
Definition: meta.hpp:1148
Tiny meta-programming library.
Definition: overload.hpp:154
Definition: overload.hpp:60