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120 lines
3.4 KiB
C++
120 lines
3.4 KiB
C++
/*=============================================================================
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Copyright (c) 2015 Paul Fultz II
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combine.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 FIT_GUARD_COMBINE_H
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#define FIT_GUARD_COMBINE_H
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/// combine
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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 `combine` function adaptor combines several functions together with
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/// their arguments. It essentially zips each function with an argument before
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/// calling the main function.
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///
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/// Synopsis
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/// --------
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///
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/// template<class F, class... Gs>
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/// constexpr combine_adaptor<F, Gs...> combine(F f, Gs... gs);
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///
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/// Semantics
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/// ---------
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///
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/// assert(combine(f, gs...)(xs...) == f(gs(xs)...));
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///
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/// Requirements
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/// ------------
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///
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/// F and Gs must be:
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///
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/// * [Callable](concepts.md#callable)
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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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/// auto f = fit::combine(
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/// fit::construct<std::tuple>(),
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/// fit::capture(1)(fit::construct<std::pair>()),
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/// fit::capture(2)(fit::construct<std::pair>()));
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/// assert(f(3, 7) == std::make_tuple(std::make_pair(1, 3), std::make_pair(2, 7)));
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///
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#include <fit/pack.hpp>
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#include <fit/always.hpp>
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#include <fit/detail/callable_base.hpp>
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#include <fit/detail/make.hpp>
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namespace fit { namespace detail {
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template<class S, class F, class... Gs>
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struct combine_adaptor_base;
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template<std::size_t... Ns, class F, class... Gs>
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struct combine_adaptor_base<seq<Ns...>, F, Gs...>
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: F, pack_base<seq<Ns...>, Gs...>
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{
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typedef pack_base<seq<Ns...>, Gs...> base_type;
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FIT_INHERIT_DEFAULT(combine_adaptor_base, base_type, F)
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template<class X, class... Xs,
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FIT_ENABLE_IF_CONSTRUCTIBLE(F, X),
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FIT_ENABLE_IF_CONSTRUCTIBLE(base_type, Xs...)>
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constexpr combine_adaptor_base(X&& x, Xs&&... xs)
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: F(FIT_FORWARD(X)(x)), base_type(FIT_FORWARD(Xs)(xs)...)
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{}
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template<class... Ts>
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constexpr const F& base_function(Ts&&... xs) const
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{
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return always_ref(*this)(xs...);
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}
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FIT_RETURNS_CLASS(combine_adaptor_base);
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// Result needs to be calculated in a separate class to avoid confusing the
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// compiler on MSVC
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#if FIT_NO_EXPRESSION_SFINAE || FIT_HAS_MANUAL_DEDUCTION
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template<class... Ts>
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struct combine_result
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: result_of<const F&, result_of<const Gs&, id_<Ts>>...>
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{};
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#endif
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template<class... Ts>
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#if FIT_NO_EXPRESSION_SFINAE || FIT_HAS_MANUAL_DEDUCTION
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constexpr typename combine_result<Ts...>::type
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#else
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constexpr auto
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#endif
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operator()(Ts&&... xs) const FIT_SFINAE_MANUAL_RETURNS
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(
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(FIT_MANGLE_CAST(const F&)(FIT_CONST_THIS->base_function(xs...)))
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(alias_value<pack_tag<seq<Ns>, Gs...>, Gs>(*FIT_CONST_THIS, xs)(FIT_FORWARD(Ts)(xs))...)
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);
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};
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}
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template<class F, class... Gs>
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struct combine_adaptor
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: detail::combine_adaptor_base<typename detail::gens<sizeof...(Gs)>::type, detail::callable_base<F>, detail::callable_base<Gs>...>
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{
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typedef detail::combine_adaptor_base<typename detail::gens<sizeof...(Gs)>::type, detail::callable_base<F>, detail::callable_base<Gs>...> base_type;
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FIT_INHERIT_CONSTRUCTOR(combine_adaptor, base_type)
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};
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FIT_DECLARE_STATIC_VAR(combine, detail::make<combine_adaptor>);
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} // namespace fit
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#endif
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