1/*============================================================================= 2 Copyright (c) 2015 Paul Fultz II 3 unpack.h 4 Distributed under the Boost Software License, Version 1.0. (See accompanying 5 file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) 6==============================================================================*/ 7 8#ifndef BOOST_HOF_GUARD_UNPACK_H 9#define BOOST_HOF_GUARD_UNPACK_H 10 11/// unpack 12/// ====== 13/// 14/// Description 15/// ----------- 16/// 17/// The `unpack` function adaptor takes a sequence and uses the elements of 18/// the sequence for the arguments to the function. Multiple sequences can be 19/// passed to the function. All elements from each sequence will be passed 20/// into the function. 21/// 22/// 23/// Synopsis 24/// -------- 25/// 26/// template<class F> 27/// unpack_adaptor<F> unpack(F f); 28/// 29/// Requirements 30/// ------------ 31/// 32/// F must be: 33/// 34/// * [ConstInvocable](ConstInvocable) 35/// * MoveConstructible 36/// 37/// Example 38/// ------- 39/// 40/// #include <boost/hof.hpp> 41/// #include <cassert> 42/// using namespace boost::hof; 43/// 44/// struct sum 45/// { 46/// template<class T, class U> 47/// T operator()(T x, U y) const 48/// { 49/// return x+y; 50/// } 51/// }; 52/// 53/// int main() { 54/// int r = unpack(sum())(std::make_tuple(3,2)); 55/// assert(r == 5); 56/// } 57/// 58/// References 59/// ---------- 60/// 61/// * [std::apply](http://en.cppreference.com/w/cpp/utility/apply) - C++17 function to unpack a tuple 62/// * [`unpack_sequence`](unpack_sequence) 63/// 64 65#include <boost/hof/unpack_sequence.hpp> 66#include <boost/hof/is_unpackable.hpp> 67#include <boost/hof/detail/seq.hpp> 68#include <boost/hof/capture.hpp> 69#include <boost/hof/always.hpp> 70#include <boost/hof/reveal.hpp> 71#include <boost/hof/detail/and.hpp> 72#include <boost/hof/detail/delegate.hpp> 73#include <boost/hof/detail/holder.hpp> 74#include <boost/hof/detail/move.hpp> 75#include <boost/hof/detail/make.hpp> 76#include <boost/hof/detail/static_const_var.hpp> 77 78namespace boost { namespace hof { 79 80namespace detail { 81 82template<class F, class Sequence> 83constexpr auto unpack_simple(F&& f, Sequence&& s) BOOST_HOF_RETURNS 84( 85 detail::unpack_impl(BOOST_HOF_FORWARD(F)(f), BOOST_HOF_FORWARD(Sequence)(s)) 86) 87 88template<class F, class... Sequences> 89constexpr auto unpack_join(F&& f, Sequences&&... s) BOOST_HOF_RETURNS 90( 91 boost::hof::pack_join(unpack_simple(boost::hof::pack_forward, BOOST_HOF_FORWARD(Sequences)(s))...)(BOOST_HOF_FORWARD(F)(f)) 92); 93 94} 95 96template<class F> 97struct unpack_adaptor : detail::callable_base<F> 98{ 99 typedef unpack_adaptor fit_rewritable1_tag; 100 BOOST_HOF_INHERIT_CONSTRUCTOR(unpack_adaptor, detail::callable_base<F>); 101 102 template<class... Ts> 103 constexpr const detail::callable_base<F>& base_function(Ts&&... xs) const noexcept 104 { 105 return boost::hof::always_ref(*this)(xs...); 106 } 107 108 struct unpack_failure 109 { 110 template<class Failure> 111 struct apply 112 { 113 struct deducer 114 { 115 template<class... Ts> 116 typename Failure::template of<Ts...> operator()(Ts&&...) const; 117 }; 118 119 template<class T, class=typename std::enable_if<( 120 is_unpackable<T>::value 121 )>::type> 122 static auto deduce(T&& x) 123 BOOST_HOF_RETURNS 124 ( 125 boost::hof::detail::unpack_simple(deducer(), BOOST_HOF_FORWARD(T)(x)) 126 ); 127 128 template<class T, class... Ts, class=typename std::enable_if<( 129 is_unpackable<T>::value && BOOST_HOF_AND_UNPACK(is_unpackable<Ts>::value) 130 )>::type> 131 static auto deduce(T&& x, Ts&&... xs) BOOST_HOF_RETURNS 132 ( 133 boost::hof::detail::unpack_join(deducer(), BOOST_HOF_FORWARD(T)(x), BOOST_HOF_FORWARD(Ts)(xs)...) 134 ); 135#ifdef _MSC_VER 136 template<class... Ts> 137 struct nop_failure; 138 template<class... Ts, class=typename std::enable_if<( 139 !BOOST_HOF_AND_UNPACK(is_unpackable<Ts>::value) 140 )>::type> 141 static as_failure<nop_failure> deduce(Ts&&... xs); 142#endif 143 template<class... Ts> 144 struct of 145#if (defined(__GNUC__) && !defined (__clang__) && __GNUC__ == 4 && __GNUC_MINOR__ < 7) || defined (_MSC_VER) 146 : std::enable_if<true, decltype(apply::deduce(std::declval<Ts>()...))>::type 147#else 148 : decltype(apply::deduce(std::declval<Ts>()...)) 149#endif 150 {}; 151 }; 152 }; 153 154 struct failure 155 : failure_map<unpack_failure, detail::callable_base<F>> 156 {}; 157 158 BOOST_HOF_RETURNS_CLASS(unpack_adaptor); 159 template<class T, class=typename std::enable_if<( 160 is_unpackable<T>::value 161 )>::type> 162 constexpr auto operator()(T&& x) const 163 BOOST_HOF_RETURNS 164 ( 165 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)) 166 ); 167 168 template<class T, class... Ts, class=typename std::enable_if<( 169 is_unpackable<T>::value && BOOST_HOF_AND_UNPACK(is_unpackable<Ts>::value) 170 )>::type> 171 constexpr auto operator()(T&& x, Ts&&... xs) const BOOST_HOF_RETURNS 172 ( 173 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)...) 174 ); 175}; 176 177BOOST_HOF_DECLARE_STATIC_VAR(unpack, detail::make<unpack_adaptor>); 178 179}} // namespace boost::hof 180 181#endif 182