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