1/*=============================================================================
2 Copyright (c) 2012 Paul Fultz II
3 match.h
4 Distributed under the Boost Software License, Version 1.0. (See accompanying
5 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
6==============================================================================*/
7
8#ifndef BOOST_HOF_GUARD_FUNCTION_OVERLOAD_H
9#define BOOST_HOF_GUARD_FUNCTION_OVERLOAD_H
10
11/// match
12/// =====
13///
14/// Description
15/// -----------
16///
17/// The `match` function adaptor combines several functions together and
18/// resolves which one should be called by using C++ overload resolution. This
19/// is different than the [`first_of`](/include/boost/hof/conditional) adaptor which resolves
20/// them based on order.
21///
22/// Synopsis
23/// --------
24///
25/// template<class... Fs>
26/// constexpr match_adaptor<Fs...> match(Fs...fs);
27///
28/// Requirements
29/// ------------
30///
31/// Fs must be:
32///
33/// * [ConstInvocable](ConstInvocable)
34/// * MoveConstructible
35///
36/// Example
37/// -------
38///
39/// #include <boost/hof.hpp>
40/// using namespace boost::hof;
41///
42/// struct int_class
43/// {
44/// int operator()(int) const
45/// {
46/// return 1;
47/// }
48/// };
49///
50/// struct foo
51/// {};
52///
53/// struct foo_class
54/// {
55/// foo operator()(foo) const
56/// {
57/// return foo();
58/// }
59/// };
60///
61/// typedef match_adaptor<int_class, foo_class> fun;
62///
63/// static_assert(std::is_same<int, decltype(fun()(1))>::value, "Failed match");
64/// static_assert(std::is_same<foo, decltype(fun()(foo()))>::value, "Failed match");
65///
66/// int main() {}
67///
68/// References
69/// ----------
70///
71/// * [POO51](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0051r2.pdf) - Proposal for C++
72/// Proposal for C++ generic overload function
73///
74
75#include <boost/hof/reveal.hpp>
76#include <boost/hof/detail/callable_base.hpp>
77#include <boost/hof/detail/delegate.hpp>
78#include <boost/hof/detail/move.hpp>
79#include <boost/hof/detail/make.hpp>
80#include <boost/hof/detail/static_const_var.hpp>
81
82namespace boost { namespace hof {
83
84template<class...Fs> struct match_adaptor;
85
86template<class F, class...Fs>
87struct match_adaptor<F, Fs...> : detail::callable_base<F>, match_adaptor<Fs...>
88{
89 typedef match_adaptor<Fs...> base;
90 typedef match_adaptor fit_rewritable_tag;
91
92 struct failure
93 : failure_for<detail::callable_base<F>, Fs...>
94 {};
95
96 BOOST_HOF_INHERIT_DEFAULT(match_adaptor, detail::callable_base<F>, base);
97
98 template<class X, class... Xs, BOOST_HOF_ENABLE_IF_CONVERTIBLE(X, detail::callable_base<F>), BOOST_HOF_ENABLE_IF_CONSTRUCTIBLE(base, Xs...)>
99 constexpr match_adaptor(X&& f1, Xs&& ... fs)
100 : detail::callable_base<F>(BOOST_HOF_FORWARD(X)(f1)), base(BOOST_HOF_FORWARD(Xs)(fs)...)
101 {}
102
103 using F::operator();
104 using base::operator();
105};
106
107template<class F>
108struct match_adaptor<F> : detail::callable_base<F>
109{
110 typedef detail::callable_base<F> base;
111 typedef match_adaptor fit_rewritable_tag;
112 using F::operator();
113
114 BOOST_HOF_INHERIT_CONSTRUCTOR(match_adaptor, detail::callable_base<F>);
115};
116
117BOOST_HOF_DECLARE_STATIC_VAR(match, detail::make<match_adaptor>);
118
119}} // namespace boost::hof
120
121#endif
122

source code of boost/libs/hof/include/boost/hof/match.hpp