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363 lines
9.5 KiB
C++
363 lines
9.5 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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/// * [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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/// 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 whether 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 my_sequence;
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///
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/// namespace fit {
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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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///
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#include <fit/returns.hpp>
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#include <tuple>
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#include <fit/detail/seq.hpp>
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#include <fit/capture.hpp>
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#include <fit/always.hpp>
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#include <fit/reveal.hpp>
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#include <fit/detail/and.hpp>
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#include <fit/detail/delegate.hpp>
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#include <fit/detail/holder.hpp>
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#include <fit/detail/move.hpp>
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#include <fit/detail/make.hpp>
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#include <fit/detail/static_const_var.hpp>
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#ifndef FIT_CHECK_UNPACK_SEQUENCE
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#define FIT_CHECK_UNPACK_SEQUENCE 1
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#endif
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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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struct unpack_impl_f
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{
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template<class F, class Sequence>
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constexpr auto operator()(F&& f, Sequence&& s) const 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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};
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FIT_DECLARE_STATIC_VAR(unpack_impl, unpack_impl_f);
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struct private_unpack_type {};
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#if FIT_CHECK_UNPACK_SEQUENCE
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template<class Sequence>
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struct unpack_impl_result
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{
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static_assert(fit::is_callable<unpack_impl_f, decltype(always(private_unpack_type())), Sequence>::value,
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"Unpack is invalid for this sequence. The function used to unpack this sequence is not callable."
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);
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typedef decltype(unpack_impl(always(private_unpack_type()), std::declval<Sequence>())) type;
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};
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template<class Sequence>
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struct is_proper_sequence
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: std::is_same<
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private_unpack_type,
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typename unpack_impl_result<Sequence>::type
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>
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{};
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#endif
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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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#if FIT_CHECK_UNPACK_SEQUENCE
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static_assert(is_proper_sequence<Sequence>::value,
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"Unpack is invalid for this sequence. The function used to unpack this sequence does not invoke the function."
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);
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#endif
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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_simple(F&& f, Sequence&& s) FIT_RETURNS
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(
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unpack_impl(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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fit::pack_join(unpack_simple(fit::pack_forward, FIT_FORWARD(Sequences)(s))...)(FIT_FORWARD(F)(f))
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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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#if FIT_CHECK_UNPACK_SEQUENCE
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typedef detail::is_unpackable_impl<
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typename std::remove_cv<typename std::remove_reference<Sequence>::type>::type
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> base;
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typedef std::conditional<base::value, detail::is_proper_sequence<Sequence>, std::true_type> check;
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static_assert(check::type::value,
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"Unpack is invalid for this sequence. The function used to unpack this sequence does not invoke the function."
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);
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#endif
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};
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template<class F>
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struct unpack_adaptor : detail::callable_base<F>
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{
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typedef unpack_adaptor fit_rewritable1_tag;
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FIT_INHERIT_CONSTRUCTOR(unpack_adaptor, detail::callable_base<F>);
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template<class... Ts>
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constexpr const detail::callable_base<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_simple(deducer(), FIT_FORWARD(T)(x))
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);
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template<class T, class... Ts, class=typename std::enable_if<(
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is_unpackable<T>::value && FIT_AND_UNPACK(is_unpackable<Ts>::value)
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)>::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, detail::callable_base<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_simple(FIT_MANGLE_CAST(const detail::callable_base<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<(
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is_unpackable<T>::value && FIT_AND_UNPACK(is_unpackable<Ts>::value)
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)>::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 detail::callable_base<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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#if (defined(__GNUC__) && !defined (__clang__) && __GNUC__ == 4 && __GNUC_MINOR__ < 7)
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template<std::size_t I, class Tuple>
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struct tuple_element_return
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: std::tuple_element<I, Tuple>
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{};
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template<std::size_t I, class Tuple>
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struct tuple_element_return<I, Tuple&>
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: std::add_lvalue_reference<typename tuple_element_return<I, Tuple>::type>
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{};
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template<std::size_t I, class Tuple>
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struct tuple_element_return<I, Tuple&&>
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: std::add_rvalue_reference<typename tuple_element_return<I, Tuple>::type>
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{};
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template<std::size_t I, class Tuple>
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struct tuple_element_return<I, const Tuple>
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: std::add_const<typename tuple_element_return<I, Tuple>::type>
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{};
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template< std::size_t I, class Tuple, class R = typename tuple_element_return<I, Tuple&&>::type >
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R tuple_get( Tuple&& t )
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{
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return (R&&)(std::get<I>(fit::forward<Tuple>(t)));
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}
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#define FIT_UNPACK_TUPLE_GET fit::detail::tuple_get
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#else
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#define FIT_UNPACK_TUPLE_GET std::get
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#endif
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template<class F, class T, std::size_t ...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(
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FIT_AUTO_FORWARD(FIT_UNPACK_TUPLE_GET<N>(FIT_AUTO_FORWARD(t)))...
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)
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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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fit::detail::unpack_pack_base(FIT_FORWARD(F)(f), FIT_FORWARD(P)(p))
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);
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};
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} // namespace fit
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#endif
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