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181 lines
5.5 KiB
181 lines
5.5 KiB
/*============================================================================= |
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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 BOOST_HOF_GUARD_UNPACK_H |
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#define BOOST_HOF_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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/// * [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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/// #include <cassert> |
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/// using namespace boost::hof; |
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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 main() { |
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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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/// References |
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/// ---------- |
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/// |
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/// * [std::apply](http://en.cppreference.com/w/cpp/utility/apply) - C++17 function to unpack a tuple |
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/// * [`unpack_sequence`](unpack_sequence) |
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/// |
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#include <boost/hof/unpack_sequence.hpp> |
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#include <boost/hof/is_unpackable.hpp> |
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#include <boost/hof/detail/seq.hpp> |
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#include <boost/hof/capture.hpp> |
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#include <boost/hof/always.hpp> |
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#include <boost/hof/reveal.hpp> |
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#include <boost/hof/detail/and.hpp> |
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#include <boost/hof/detail/delegate.hpp> |
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#include <boost/hof/detail/holder.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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namespace detail { |
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template<class F, class Sequence> |
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constexpr auto unpack_simple(F&& f, Sequence&& s) BOOST_HOF_RETURNS |
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( |
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detail::unpack_impl(BOOST_HOF_FORWARD(F)(f), BOOST_HOF_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) BOOST_HOF_RETURNS |
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( |
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boost::hof::pack_join(unpack_simple(boost::hof::pack_forward, BOOST_HOF_FORWARD(Sequences)(s))...)(BOOST_HOF_FORWARD(F)(f)) |
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); |
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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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BOOST_HOF_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 noexcept |
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{ |
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return boost::hof::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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BOOST_HOF_RETURNS |
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( |
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boost::hof::detail::unpack_simple(deducer(), BOOST_HOF_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 && BOOST_HOF_AND_UNPACK(is_unpackable<Ts>::value) |
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)>::type> |
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static auto deduce(T&& x, Ts&&... xs) BOOST_HOF_RETURNS |
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( |
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boost::hof::detail::unpack_join(deducer(), BOOST_HOF_FORWARD(T)(x), BOOST_HOF_FORWARD(Ts)(xs)...) |
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); |
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#ifdef _MSC_VER |
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template<class... Ts> |
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struct nop_failure; |
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template<class... Ts, class=typename std::enable_if<( |
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!BOOST_HOF_AND_UNPACK(is_unpackable<Ts>::value) |
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)>::type> |
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static as_failure<nop_failure> deduce(Ts&&... xs); |
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#endif |
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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) || defined (_MSC_VER) |
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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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BOOST_HOF_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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BOOST_HOF_RETURNS |
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( |
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boost::hof::detail::unpack_simple(BOOST_HOF_MANGLE_CAST(const detail::callable_base<F>&)(BOOST_HOF_CONST_THIS->base_function(x)), BOOST_HOF_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 && BOOST_HOF_AND_UNPACK(is_unpackable<Ts>::value) |
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)>::type> |
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constexpr auto operator()(T&& x, Ts&&... xs) const BOOST_HOF_RETURNS |
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( |
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boost::hof::detail::unpack_join(BOOST_HOF_MANGLE_CAST(const detail::callable_base<F>&)(BOOST_HOF_CONST_THIS->base_function(x)), BOOST_HOF_FORWARD(T)(x), BOOST_HOF_FORWARD(Ts)(xs)...) |
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); |
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}; |
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BOOST_HOF_DECLARE_STATIC_VAR(unpack, detail::make<unpack_adaptor>); |
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}} // namespace boost::hof |
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#endif
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