invocation_traits.h

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/*  Copyright (c) SILVERCODERS Ltd, http://silvercoders.com                                                                                  */
/*  Project homepage: https://github.com/docwire/docwire                                                                                     */
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#ifndef DOCWIRE_INVOCATION_TRAITS_H
#define DOCWIRE_INVOCATION_TRAITS_H
 
#include <boost/callable_traits/args.hpp>
#include <boost/callable_traits/return_type.hpp>
#include <tuple>
 
namespace docwire::invocation_traits
{
 
template <typename T>
struct args
{
 
  template <typename F>
  struct args_impl
  {
    using type = boost::callable_traits::args_t<F>;
  };
 
  template <typename F>
    requires requires { typename F::invocation_args_t; }
  struct args_impl<F>
  {
    using type = typename F::invocation_args_t;
  };
 
  using type = typename args_impl<T>::type;
};
 
template <typename T>
using args_t = typename args<T>::type;
 
template <typename T>
inline constexpr std::size_t arity_v = std::tuple_size_v<args_t<T>>;
 
template <typename T>
struct result
{
 
  template <typename F>
  struct result_impl
  {
    using type = boost::callable_traits::return_type_t<F>;
  };
 
  template <typename F>
    requires requires { typename F::invocation_result_t; }
  struct result_impl<F>
  {
    using type = typename F::invocation_result_t;
  };
 
    using type = typename result_impl<T>::type;
};
 
template <typename T>
using result_t = typename result<T>::type;
 
template <typename T>
struct is_invocable
{
  static constexpr bool value =
    requires { typename boost::callable_traits::args_t<T>; } ||
    requires { typename std::decay_t<T>::invocation_args_t; };
};
 
template <typename T>
inline constexpr bool is_invocable_v = is_invocable<T>::value;
 
} // namespace docwire::invocation_traits
 
#endif //DOCWIRE_INVOCATION_TRAITS_H