key_value.hpp

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//
// Created by YongGyu Lee on 2/22/24.
//
 
#ifndef VCCC_UTILITY_KEY_VALUE_HPP
#define VCCC_UTILITY_KEY_VALUE_HPP
 
#include <cstddef>
#include <tuple>
#include <utility>
 
#include "vccc/__core/inline_or_static.hpp"
#include "vccc/__tuple/tuple_like.hpp"
#include "vccc/__type_traits/conjunction.hpp"
#include "vccc/__type_traits/remove_cvref.hpp"
 
namespace vccc {
namespace detail {
 
template<std::size_t I>
struct element_niebloid {
  template<typename T, std::enable_if_t<conjunction<
      tuple_like<T>,
      internal::tuple_size_greater_than<remove_cvref_t<T>, I>
  >::value, int> = 0>
  constexpr decltype(auto) operator()(T&& t) const noexcept {
    return std::get<I>(std::forward<T>(t));
  }
};
 
} // namespace detail
 
VCCC_INLINE_OR_STATIC constexpr detail::element_niebloid<0> key;
VCCC_INLINE_OR_STATIC constexpr detail::element_niebloid<0> first;
VCCC_INLINE_OR_STATIC constexpr detail::element_niebloid<1> value;
VCCC_INLINE_OR_STATIC constexpr detail::element_niebloid<1> second;
 
template<std::size_t I>
VCCC_INLINE_OR_STATIC constexpr detail::element_niebloid<I> element;
 
} // namespace vccc
 
 
#endif // VCCC_UTILITY_KEY_VALUE_HPP