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 Hu Chunming
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/*=============================================================================
Copyright (c) 2012 Paul Fultz II
match.h
Distributed under the Boost Software License, Version 1.0. (See accompanying
file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
==============================================================================*/
#ifndef BOOST_HOF_GUARD_FUNCTION_OVERLOAD_H
#define BOOST_HOF_GUARD_FUNCTION_OVERLOAD_H
/// match
/// =====
///
/// Description
/// -----------
///
/// The `match` function adaptor combines several functions together and
/// resolves which one should be called by using C++ overload resolution. This
/// is different than the [`first_of`](/include/boost/hof/conditional) adaptor which resolves
/// them based on order.
///
/// Synopsis
/// --------
///
/// template<class... Fs>
/// constexpr match_adaptor<Fs...> match(Fs...fs);
///
/// Requirements
/// ------------
///
/// Fs must be:
///
/// * [ConstInvocable](ConstInvocable)
/// * MoveConstructible
///
/// Example
/// -------
///
/// #include <boost/hof.hpp>
/// using namespace boost::hof;
///
/// struct int_class
/// {
/// int operator()(int) const
/// {
/// return 1;
/// }
/// };
///
/// struct foo
/// {};
///
/// struct foo_class
/// {
/// foo operator()(foo) const
/// {
/// return foo();
/// }
/// };
///
/// typedef match_adaptor<int_class, foo_class> fun;
///
/// static_assert(std::is_same<int, decltype(fun()(1))>::value, "Failed match");
/// static_assert(std::is_same<foo, decltype(fun()(foo()))>::value, "Failed match");
///
/// int main() {}
///
/// References
/// ----------
///
/// * [POO51](http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0051r2.pdf) - Proposal for C++
/// Proposal for C++ generic overload function
///
#include <boost/hof/reveal.hpp>
#include <boost/hof/detail/callable_base.hpp>
#include <boost/hof/detail/delegate.hpp>
#include <boost/hof/detail/move.hpp>
#include <boost/hof/detail/make.hpp>
#include <boost/hof/detail/static_const_var.hpp>
namespace boost { namespace hof {
template<class...Fs> struct match_adaptor;
template<class F, class...Fs>
struct match_adaptor<F, Fs...> : detail::callable_base<F>, match_adaptor<Fs...>
{
typedef match_adaptor<Fs...> base;
typedef match_adaptor fit_rewritable_tag;
struct failure
: failure_for<detail::callable_base<F>, Fs...>
{};
BOOST_HOF_INHERIT_DEFAULT(match_adaptor, detail::callable_base<F>, base);
template<class X, class... Xs, BOOST_HOF_ENABLE_IF_CONVERTIBLE(X, detail::callable_base<F>), BOOST_HOF_ENABLE_IF_CONSTRUCTIBLE(base, Xs...)>
constexpr match_adaptor(X&& f1, Xs&& ... fs)
: detail::callable_base<F>(BOOST_HOF_FORWARD(X)(f1)), base(BOOST_HOF_FORWARD(Xs)(fs)...)
{}
using F::operator();
using base::operator();
};
template<class F>
struct match_adaptor<F> : detail::callable_base<F>
{
typedef detail::callable_base<F> base;
typedef match_adaptor fit_rewritable_tag;
using F::operator();
BOOST_HOF_INHERIT_CONSTRUCTOR(match_adaptor, detail::callable_base<F>);
};
BOOST_HOF_DECLARE_STATIC_VAR(match, detail::make<match_adaptor>);
}} // namespace boost::hof
#endif
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