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268 lines
6.6 KiB
C++
268 lines
6.6 KiB
C++
/*=============================================================================
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Copyright (c) 2015 Paul Fultz II
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unpack.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_UNPACK_H
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#define FIT_GUARD_UNPACK_H
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/// unpack
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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 `unpack` function adaptor takes a sequence and uses the elements of
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/// the sequence for the arguments to the function. Multiple sequences can be
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/// passed to the function. All elements from each sequence will be passed
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/// into the function.
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///
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///
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/// Synopsis
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/// --------
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///
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/// template<class F>
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/// unpack_adaptor<F> unpack(F f);
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///
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/// Requirements
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/// ------------
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///
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/// F must be:
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///
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/// FunctionObject
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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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/// struct sum
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/// {
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/// template<class T, class U>
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/// T operator()(T x, U y) const
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/// {
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/// return x+y;
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/// }
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/// };
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///
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/// int r = unpack(sum())(std::make_tuple(3,2));
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/// assert(r == 5);
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///
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///
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/// is_unpackable
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/// =============
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///
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/// This is a trait that can be used to detect whethet the type can be called
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/// with `unpack`.
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///
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/// Synopsis
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/// --------
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///
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/// template<class T>
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/// struct is_unpackable;
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///
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/// Example
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/// -------
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///
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/// static_assert(fit::is_unpackable<std::tuple<int>>::value, "Failed");
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///
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/// unpack_sequence
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/// ===============
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///
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/// How to unpack a sequence can be defined by specializing `unpack_sequence`.
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/// By default, `std::tuple` can be used with unpack.
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///
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/// Synopsis
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/// --------
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///
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/// template<class Sequence, class=void>
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/// struct unpack_sequence;
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///
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/// Example
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/// -------
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///
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/// template<class... Ts>
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/// struct unpack_sequence<my_sequence<Ts...>>
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/// {
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/// template<class F, class Sequence>
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/// constexpr static auto apply(F&& f, Sequence&& s) FIT_RETURNS
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/// (
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/// s(std::forward<F>(f))
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/// );
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/// };
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///
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#include <fit/returns.h>
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#include <tuple>
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#include <fit/detail/seq.h>
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#include <fit/capture.h>
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#include <fit/always.h>
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#include <fit/reveal.h>
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#include <fit/detail/and.h>
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#include <fit/detail/delegate.h>
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#include <fit/detail/holder.h>
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#include <fit/detail/move.h>
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#include <fit/detail/make.h>
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#include <fit/detail/static_const_var.h>
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namespace fit {
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template<class Sequence, class=void>
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struct unpack_sequence
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{
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typedef void not_unpackable;
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};
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namespace detail {
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template<class Sequence, class=void>
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struct is_unpackable_impl
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: std::true_type
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{};
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template<class Sequence>
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struct is_unpackable_impl<Sequence, typename detail::holder<
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typename unpack_sequence<Sequence>::not_unpackable
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>::type>
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: std::false_type
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{};
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template<class F, class Sequence>
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constexpr auto unpack_impl(F&& f, Sequence&& s) FIT_RETURNS
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(
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fit::unpack_sequence<typename std::remove_cv<typename std::remove_reference<Sequence>::type>::type>::
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apply(fit::forward<F>(f), fit::forward<Sequence>(s))
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);
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template<class F, class... Sequences>
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constexpr auto unpack_join(F&& f, Sequences&&... s) FIT_RETURNS
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(
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unpack_impl(fit::forward<F>(f), fit::pack_join(unpack_impl(fit::pack_forward, fit::forward<Sequences>(s))...))
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);
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}
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template<class Sequence>
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struct is_unpackable
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: detail::is_unpackable_impl<
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typename std::remove_cv<typename std::remove_reference<Sequence>::type>::type
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>
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{};
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template<class F>
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struct unpack_adaptor : F
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{
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FIT_INHERIT_CONSTRUCTOR(unpack_adaptor, F);
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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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struct unpack_failure
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{
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template<class Failure>
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struct apply
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{
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struct deducer
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{
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template<class... Ts>
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typename Failure::template of<Ts...> operator()(Ts&&...) const;
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};
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template<class T, class=typename std::enable_if<(
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is_unpackable<T>::value
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)>::type>
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static auto deduce(T&& x)
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FIT_RETURNS
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(
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detail::unpack_impl(deducer(), fit::forward<T>(x))
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);
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template<class T, class... Ts, class=typename std::enable_if<(detail::and_<
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is_unpackable<T>, is_unpackable<Ts>...
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>::value)>::type>
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static auto deduce(T&& x, Ts&&... xs) FIT_RETURNS
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(
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detail::unpack_join(deducer(), fit::forward<T>(x), fit::forward<Ts>(xs)...)
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);
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template<class... Ts>
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struct of
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#if defined(__GNUC__) && !defined (__clang__) && __GNUC__ == 4 && __GNUC_MINOR__ < 7
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: std::enable_if<true, decltype(apply::deduce(std::declval<Ts>()...))>::type
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#else
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: decltype(apply::deduce(std::declval<Ts>()...))
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#endif
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{};
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};
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};
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struct failure
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: failure_map<unpack_failure, F>
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{};
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FIT_RETURNS_CLASS(unpack_adaptor);
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template<class T, class=typename std::enable_if<(
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is_unpackable<T>::value
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)>::type>
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constexpr auto operator()(T&& x) const
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FIT_RETURNS
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(
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detail::unpack_impl(FIT_MANGLE_CAST(const F&)(FIT_CONST_THIS->base_function(x)), fit::forward<T>(x))
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);
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template<class T, class... Ts, class=typename std::enable_if<(detail::and_<
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is_unpackable<T>, is_unpackable<Ts>...
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>::value)>::type>
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constexpr auto operator()(T&& x, Ts&&... xs) const FIT_RETURNS
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(
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detail::unpack_join(FIT_MANGLE_CAST(const F&)(FIT_CONST_THIS->base_function(x)), fit::forward<T>(x), fit::forward<Ts>(xs)...)
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);
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};
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FIT_DECLARE_STATIC_VAR(unpack, detail::make<unpack_adaptor>);
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namespace detail {
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template<class Sequence>
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constexpr typename gens<std::tuple_size<Sequence>::value>::type
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make_tuple_gens(const Sequence&)
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{
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return {};
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}
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template<class F, class T, int ...N>
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constexpr auto unpack_tuple(F&& f, T && t, seq<N...>) FIT_RETURNS
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(
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f(FIT_AUTO_FORWARD(std::get<N>(t))...)
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);
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}
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template<class... Ts>
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struct unpack_sequence<std::tuple<Ts...>>
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{
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template<class F, class S>
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constexpr static auto apply(F&& f, S&& t) FIT_RETURNS
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(
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detail::unpack_tuple(fit::forward<F>(f), fit::forward<S>(t), detail::make_tuple_gens(t))
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);
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};
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template<class T, class... Ts>
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struct unpack_sequence<detail::pack_base<T, Ts...>>
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{
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template<class F, class P>
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constexpr static auto apply(F&& f, P&& p) FIT_RETURNS
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(
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p(fit::forward<F>(f))
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);
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};
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}
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#endif |