conditional_types.h

Go to the documentation of this file.

// =====================================================================================================================
//  fennec, a free and open source game engine
//  Copyright © 2025  Medusa Slockbower
//
//  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 should have received a copy of the GNU General Public License
//  along with this program.  If not, see <https://www.gnu.org/licenses/>.
// =====================================================================================================================
 
 
 
#ifndef FENNEC_LANG_CONDITIONAL_TYPES_H
#define FENNEC_LANG_CONDITIONAL_TYPES_H
 
#include <fennec/lang/type_identity.h>
 
 
namespace fennec
{
 
// fennec::conditional =================================================================================================
 
template<bool B, typename TrueT, typename FalseT>
struct conditional;
 
 
template<bool B, typename TrueT, typename FalseT>
using conditional_t
    = typename conditional<B, TrueT, FalseT>::type;
 
 
// specialization of fennec::conditional for `true` case
template<typename T, typename F>
struct conditional<true, T, F> : type_identity<T>{};
 
 
// specialization of fennec::conditional for `false` case
template<typename T, typename F>
struct conditional<false, T, F> : type_identity<F>{};
 
 
// fennec::detect ======================================================================================================
 
template<typename DefaultT, template<typename...> typename DetectT, typename...ArgsT>
struct detect
{
    using type = DefaultT;
    static constexpr bool is_detected = false;
};
 
template<typename DefaultT, template<typename...> typename DetectT, typename...ArgsT>
using detect_t = typename detect<DefaultT, DetectT, ArgsT...>::type;
 
 
// true case
template<typename DefaultT, template<typename...> typename DetectT, typename...ArgsT>
    requires requires { typename DetectT<ArgsT...>; }
struct detect<DefaultT, DetectT, ArgsT...>
{
    using type = DetectT<ArgsT...>;
    static constexpr bool is_detected = true;
};
 
 
// fennec::enable_if ===================================================================================================
 
template<bool B, typename T = void>
struct enable_if {};
 
template<bool B, typename T = void>
using enable_if_t = typename enable_if<B, T>::type;
 
// true case
template<typename T>
struct enable_if<true, T> { using type = T; };
 
}
 
#endif // FENNEC_LANG_CONDITIONAL_TYPES_H