leaf/detail/function_traits.hpp

0001 #ifndef BOOST_LEAF_DETAIL_FUNCTION_TRAITS_HPP_INCLUDED
0002 #define BOOST_LEAF_DETAIL_FUNCTION_TRAITS_HPP_INCLUDED
0003
0004 // Copyright 2018-2023 Emil Dotchevski and Reverge Studios, Inc.
0005
0006 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0007 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0008
0009 #include <boost/leaf/detail/mp11.hpp>
0010
0011 #include <tuple>
0012
0013 namespace boost { namespace leaf {
0014
0015 namespace leaf_detail
0016 {
0017     template <class T> struct remove_noexcept { using type = T; };
0018     template <class R, class... A>  struct remove_noexcept<R(*)(A...) noexcept> { using type = R(*)(A...); };
0019     template <class C, class R, class... A>  struct remove_noexcept<R(C::*)(A...) noexcept> { using type = R(C::*)(A...); };
0020     template <class C, class R, class... A>  struct remove_noexcept<R(C::*)(A...) const noexcept> { using type = R(C::*)(A...) const; };
0021
0022     template<class...>
0023     struct gcc49_workaround //Thanks Glen Fernandes
0024     {
0025         using type = void;
0026     };
0027
0028     template<class... T>
0029     using void_t = typename gcc49_workaround<T...>::type;
0030
0031     template<class F,class V=void>
0032     struct function_traits_impl
0033     {
0034         constexpr static int arity = -1;
0035     };
0036
0037     template<class F>
0038     struct function_traits_impl<F, void_t<decltype(&F::operator())>>
0039     {
0040     private:
0041
0042         using tr = function_traits_impl<typename remove_noexcept<decltype(&F::operator())>::type>;
0043
0044     public:
0045
0046         using return_type = typename tr::return_type;
0047         static constexpr int arity = tr::arity - 1;
0048
0049         using mp_args = typename leaf_detail_mp11::mp_rest<typename tr::mp_args>;
0050
0051         template <int I>
0052         struct arg:
0053             tr::template arg<I+1>
0054         {
0055         };
0056     };
0057
0058     template<class R, class... A>
0059     struct function_traits_impl<R(A...)>
0060     {
0061         using return_type = R;
0062         static constexpr int arity = sizeof...(A);
0063
0064         using mp_args = leaf_detail_mp11::mp_list<A...>;
0065
0066         template <int I>
0067         struct arg
0068         {
0069             static_assert(I < arity, "I out of range");
0070             using type = typename std::tuple_element<I,std::tuple<A...>>::type;
0071         };
0072     };
0073
0074     template<class F> struct function_traits_impl<F&> : function_traits_impl<F> { };
0075     template<class F> struct function_traits_impl<F&&> : function_traits_impl<F> { };
0076     template<class R, class... A> struct function_traits_impl<R(*)(A...)> : function_traits_impl<R(A...)> { };
0077     template<class R, class... A> struct function_traits_impl<R(* &)(A...)> : function_traits_impl<R(A...)> { };
0078     template<class R, class... A> struct function_traits_impl<R(* const &)(A...)> : function_traits_impl<R(A...)> { };
0079     template<class C, class R, class... A> struct function_traits_impl<R(C::*)(A...)> : function_traits_impl<R(C&,A...)> { };
0080     template<class C, class R, class... A> struct function_traits_impl<R(C::*)(A...) const> : function_traits_impl<R(C const &,A...)> { };
0081     template<class C, class R> struct function_traits_impl<R(C::*)> : function_traits_impl<R(C&)> { };
0082
0083     template <class F>
0084     struct function_traits: function_traits_impl<typename remove_noexcept<F>::type>
0085     {
0086     };
0087
0088     template <class F>
0089     using fn_return_type = typename function_traits<F>::return_type;
0090
0091     template <class F, int I>
0092     using fn_arg_type = typename function_traits<F>::template arg<I>::type;
0093
0094     template <class F>
0095     using fn_mp_args = typename function_traits<F>::mp_args;
0096 }
0097
0098 } }
0099
0100 #endif