boolean_testable.hpp

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//
// Created by yonggyulee on 2023/12/25.
//
 
#ifndef VCCC_CONCEPTS_BOOLEAN_TESTABLE_HPP_
#define VCCC_CONCEPTS_BOOLEAN_TESTABLE_HPP_
 
#include <type_traits>
 
#include "vccc/__concepts/convertible_to.hpp"
#include "vccc/__type_traits/conjunction.hpp"
#include "vccc/__type_traits/is_referenceable.hpp"
 
namespace vccc {
namespace detail {
 
template<typename B>
struct boolean_testable_impl : convertible_to<B, bool> {};
 
template<typename T, typename = void>
struct is_explicitly_negatable : std::false_type {};
template<typename T>
struct is_explicitly_negatable<T, void_t<decltype(!std::declval<T>())> > : std::true_type {};
 
template<
    typename B,
    bool =
        conjunction<
            is_explicitly_negatable<std::add_lvalue_reference_t<std::remove_reference_t<B>>>,
            is_explicitly_negatable<std::add_rvalue_reference_t<std::remove_reference_t<B>>>
        >::value
>
struct boolean_testable_stage_2 : std::false_type {};
 
template<typename B>
struct boolean_testable_stage_2<B, true>
    : conjunction<
        boolean_testable_impl<decltype(!std::declval< std::add_lvalue_reference_t<std::remove_reference_t<B>> >())>,
        boolean_testable_impl<decltype(!std::declval< std::add_rvalue_reference_t<std::remove_reference_t<B>> >())>
      > {};
 
template<
    typename B,
    bool = conjunction<boolean_testable_impl<B>, is_referencable<B>>::value
>
struct boolean_testable_stage_1 : std::false_type {};
 
template<typename B>
struct boolean_testable_stage_1<B, true> : boolean_testable_stage_2<B> {};
 
} // namespace detail
 
 
template<typename B>
struct boolean_testable : detail::boolean_testable_stage_1<B> {};
 
 
} // namespace vccc
 
#endif // VCCC_CONCEPTS_BOOLEAN_TESTABLE_HPP_