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 2018-2024 Emil Dotchevski and Reverge Studios, Inc.
0005 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0006 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0007
0008 #include <boost/leaf/detail/mp11.hpp>
0009
0010 #include <tuple>
0011
0012 namespace boost { namespace leaf {
0013
0014 namespace detail
0015 {
0016     template <class T> struct remove_noexcept { using type = T; };
0017     template <class R, class... A>  struct remove_noexcept<R(*)(A...) noexcept> { using type = R(*)(A...); };
0018     template <class C, class R, class... A>  struct remove_noexcept<R(C::*)(A...) noexcept> { using type = R(C::*)(A...); };
0019     template <class C, class R, class... A>  struct remove_noexcept<R(C::*)(A...) const noexcept> { using type = R(C::*)(A...) const; };
0020
0021     template<class...>
0022     struct gcc49_workaround //Thanks Glen Fernandes
0023     {
0024         using type = void;
0025     };
0026
0027     template<class... T>
0028     using void_t = typename gcc49_workaround<T...>::type;
0029
0030     template<class F,class V=void>
0031     struct function_traits_impl
0032     {
0033         constexpr static int arity = -1;
0034     };
0035
0036     template<class F>
0037     struct function_traits_impl<F, void_t<decltype(&F::operator())>>
0038     {
0039     private:
0040
0041         using tr = function_traits_impl<typename remove_noexcept<decltype(&F::operator())>::type>;
0042
0043     public:
0044
0045         using return_type = typename tr::return_type;
0046         static constexpr int arity = tr::arity - 1;
0047
0048         using mp_args = typename leaf_detail_mp11::mp_rest<typename tr::mp_args>;
0049
0050         template <int I>
0051         struct arg:
0052             tr::template arg<I+1>
0053         {
0054         };
0055     };
0056
0057     template<class R, class... A>
0058     struct function_traits_impl<R(A...)>
0059     {
0060         using return_type = R;
0061         static constexpr int arity = sizeof...(A);
0062
0063         using mp_args = leaf_detail_mp11::mp_list<A...>;
0064
0065         template <int I>
0066         struct arg
0067         {
0068             static_assert(I < arity, "I out of range");
0069             using type = typename std::tuple_element<I,std::tuple<A...>>::type;
0070         };
0071     };
0072
0073     template<class F> struct function_traits_impl<F&> : function_traits_impl<F> { };
0074     template<class F> struct function_traits_impl<F&&> : function_traits_impl<F> { };
0075     template<class R, class... A> struct function_traits_impl<R(*)(A...)> : function_traits_impl<R(A...)> { };
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(* const &)(A...)> : function_traits_impl<R(A...)> { };
0078     template<class C, class R, class... A> struct function_traits_impl<R(C::*)(A...)> : function_traits_impl<R(C&,A...)> { };
0079     template<class C, class R, class... A> struct function_traits_impl<R(C::*)(A...) const> : function_traits_impl<R(C const &,A...)> { };
0080     template<class C, class R> struct function_traits_impl<R(C::*)> : function_traits_impl<R(C&)> { };
0081
0082     template <class F>
0083     struct function_traits: function_traits_impl<typename remove_noexcept<F>::type>
0084     {
0085     };
0086
0087     template <class F>
0088     using fn_return_type = typename function_traits<F>::return_type;
0089
0090     template <class F, int I>
0091     using fn_arg_type = typename function_traits<F>::template arg<I>::type;
0092
0093     template <class F>
0094     using fn_mp_args = typename function_traits<F>::mp_args;
0095 }
0096
0097 } }
0098
0099 #endif // BOOST_LEAF_DETAIL_FUNCTION_TRAITS_HPP_INCLUDED