utl/include/utl/meta/useif.h

/*!
 * \file    useif.h
 * \brief   Template meta-programming SFINAE helpers
 *
 * \copyright
 *    Copyright (C) 2018 Christos Choutouridis <christos@choutouridis.net>\n
 *    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.\n
 *    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.\n
 *    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_useif_h__
#define __utl_meta_useif_h__

#include <utl/core/impl.h>
#include <utl/meta/operations.h>
#include <utl/meta/sfinae.h>

/*!
 * \ingroup meta
 * \addtogroup sfinae
 */
//! @{
namespace utl {
namespace meta {

   //! If same type resolves to Ret, else SFINAE
   template <typename T1, typename T2, typename Ret =T1>
   using use_if_same_t = enable_if_t<
      eval_v<same_<T1, T2>>, Ret
   >;
   //! If not same type resolves to Ret, else SFINAE
   template <typename T1, typename T2, typename Ret =T1>
   using use_if_not_same_t = enable_if_t<
      eval_v<not_same_<T1, T2>>, Ret
   >;
   //! If any type (T1 or T2) type resolves to Ret, else to SFINAE
   template <typename T1, typename... Ts>
   using use_if_any_t = enable_if_t<
      eval_v<or_<T1, Ts...>>, T1
   >;

   //! If both type (T1 and T2) type resolves to Ret, else to SFINAE
   template <typename T1, typename... Ts>
   using use_if_all_t = enable_if_t<
      eval_v<and_<T1, Ts...>>, T1
   >;

}}

//! @}

#endif /* __utl_meta_useif_h__ */