trueFalseT.hpp

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/** \file trueFalseT.hpp
 * \brief Declares and defines a true-false virtual type used for boolean template overrides
 * \ingroup utils_files
 * \author Jared R. Males (jaredmales@gmail.com)
 *
 */
 
//***********************************************************************//
// Copyright 2015, 2016, 2017, 2018 Jared R. Males (jaredmales@gmail.com)
//
// This file is part of mxlib.
//
// mxlib 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.
//
// mxlib 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 mxlib.  If not, see <http://www.gnu.org/licenses/>.
//***********************************************************************//
 
#ifndef trueFalseT_hpp
#define trueFalseT_hpp
 
namespace mx
{
 
namespace meta
{
 
/// Template declaration of a trueFalseT type.
/** The specialized types can be used for tag dispatching, that is achieving SFINAE-like behavior but with function
 * overloading when identical function signatures are desired.  This works because trueFalseT<true> and
 * trueFalseT<false> are dfferent types.
 *
 * This is a slightly simpler construct than std::true_type and std::false_type, which are derived from
 * std::integral_constant.
 *
 * This template type is not defined, only the specializations are. The specializations have a typedef of True or False,
 * accordingly, and a static const member value which evaluates to true or false accordingly.
 *
 * \tparam trueFalse bool to choose which of the specializations to invoke.
 *
 * \ingroup meta
 */
template <bool trueFalse>
struct trueFalseT;
 
/// The true specialization of trueFalseT.
/** \ingroup meta
 */
template <>
struct trueFalseT<true>
{
    typedef bool True;              ///< Typedef which can be used for SFINAE
    static const bool value = true; ///< bool member value = true
};
 
/// The false specialization of trueFalseT.
/** \ingroup meta
 */
template <>
struct trueFalseT<false>
{
    typedef bool False;              ///< Typedef which can be used for SFINAE
    static const bool value = false; ///< bool member value = false
};
 
} // namespace meta
} // namespace mx
 
#endif // trueFalseT_hpp