indirect_result_t.hpp

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//
// Created by yonggyulee on 2023/12/29.
//
 
#ifndef VCCC_ITERATOR_INDIRECT_RESULT_T_HPP
#define VCCC_ITERATOR_INDIRECT_RESULT_T_HPP
 
#include "vccc/__concepts/invocable.hpp"
#include "vccc/__functional/invoke.hpp"
#include "vccc/__iterator/indirectly_readable.hpp"
#include "vccc/__iterator/iter_reference_t.hpp"
#include "vccc/__type_traits/conjunction.hpp"
#include "vccc/__type_traits/has_typename_type.hpp"
 
namespace vccc {
namespace detail {
 
template<bool /* true */, typename F, typename... Is>
struct indirect_result_impl_2 {
  using type = invoke_result_t<F, iter_reference_t<Is>...>;
};
 
template<typename F, typename... Is>
struct indirect_result_impl_2<false, F, Is...> {};
 
template<bool /* true */, typename F, typename... Is>
struct indirect_result_impl_1
    : indirect_result_impl_2<
          invocable<F, iter_reference_t<Is>...>::value,
          F,
          Is...
      > {};
 
template<typename F, typename... Is>
struct indirect_result_impl_1<false, F, Is...> {};
 
} // namespace detail
 
 
template<typename F, typename... Is>
struct indirect_result
    : detail::indirect_result_impl_1<
          conjunction<
            indirectly_readable<Is>...,
            has_typename_type<iter_reference<Is>>...
          >::value,
          F,
          Is...
      > {};
 
template<typename F, typename... Is>
using indirect_result_t = typename indirect_result<F, Is...>::type;
 
 
} // namespace vccc
 
#endif // VCCC_ITERATOR_INDIRECT_RESULT_T_HPP