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