utl/include/utl/meta/detection.h

/*!
 * \file    detection.h
 * \brief   Detection idiom based on WG21's N4502[1] from Walter E. Brown
 *
 * [1]: www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4502.pdf
 *
 * Copyright (C) 2018-2019 Christos Choutouridis
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#ifndef __utl_meta_detection_h__
#define __utl_meta_detection_h__

#include <utl/core/impl.h>
#include <utl/meta/logical.h>
#include <type_traits>

/*!
 * \ingroup meta
 * \defgroup detection
 * Detection idiom support header.
 */
//! @{

namespace utl {
namespace meta {

   /*!
    * void_t meta-function that maps a sequence of any types to the type void
    */
   //! @{
   #if defined(UTL_WORKAROUND_CWG_1558)
      template<typename... _Ts>
      struct void_ {
         using type = void;
      };
      //! void_t type alias
      template<typename... _Ts>
      using void_t = eval<void_<_Ts...>>;
   #else
      //! void_ type alias
      template <typename...> using void_  = void;
      //! void_t type alias
      template <typename...> using void_t = void;
   #endif
   //! @}
}}
//!@}

#endif /* __utl_meta_void_h__ */