callable_traits.hpp

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// Copyright (c) 2013-2018 Commissariat à l'énergie atomique et aux énergies alternatives (CEA)
// Copyright (c) 2013-2018 Centre national de la recherche scientifique (CNRS)
// Copyright (c) 2018 Simons Foundation
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You may obtain a copy of the License at
//     https://www.gnu.org/licenses/gpl-3.0.txt
//
// Authors: Olivier Parcollet, Nils Wentzell

 
#pragma once
 
#include <cstddef>
#include <tuple>
#include <type_traits>
 
namespace triqs::utility {
 
  namespace detail {
 
    template <typename F> struct callable_traits_impl;
 
    template <typename ClassType, typename ReturnType, typename... Args> struct callable_traits_impl<ReturnType (ClassType::*)(Args...) const> {
      static constexpr int arity                 = sizeof...(Args);
      using result_type                          = ReturnType;
      template <std::size_t N> using arg_t       = std::tuple_element_t<N, std::tuple<Args...>>;
      template <std::size_t N> using decay_arg_t = std::decay_t<arg_t<N>>;
    };
 
    template <typename ClassType, typename ReturnType, typename... Args>
    struct callable_traits_impl<ReturnType (ClassType::*)(Args...)> : callable_traits_impl<ReturnType (ClassType::*)(Args...) const> {};
 
  } // namespace detail

  template <typename F> struct callable_traits : public detail::callable_traits_impl<decltype(&F::operator())> {};
 
} // namespace triqs::utility