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- /*!
- * \file selection.h
- * \brief Template meta-programming type selections.
- *
- * Copyright (C) 2018 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_selection_h__
- #define __utl_meta_selection_h__
-
- #include <utl/core/impl.h>
- #include <utl/meta/integral.h>
- #include <utl/meta/sfinae.h>
-
- /*!
- * \ingroup meta
- * \defgroup type selection
- * Type selection support header
- */
- //! @{
- namespace utl {
- namespace meta{
-
- /*!
- * Type selection
- */
- //! @{
-
- //! if_, if_c
- //! @{
- namespace detail {
- template <bool If, typename...>
- struct if_c_ {
- using type = nil_; //!< avoid ill formed result
- };
- template<typename Then>
- struct if_c_<true, Then> {
- using type = Then;
- };
- template<typename Then, typename Else>
- struct if_c_<true, Then, Else> {
- using type = Then;
- };
- template<typename Then, typename Else>
- struct if_c_<false, Then, Else> {
- using type = Else;
- };
- }
- //! Select one type or another depending on a compile-time Boolean.
- template <bool B, typename... Args>
- using if_c = type_<detail::if_c_<B, Args...>>;
-
- //! Select one type or another depending on a compile-time Boolean type
- template <typename If, typename... Args>
- using if_ = if_c<If::type::value, Args...>;
-
- //! @}
-
- /*!
- * Named type selectors
- */
- //! @{
-
- //! Select the first type of a type sequence
- template <typename T1, typename ...>
- struct first_of {
- using type = T1;
- };
- //! Select the second type of a type sequence
- template <typename T1, typename T2, typename ...>
- struct second_of {
- using type = T2;
- };
-
- //! @}
- }}
-
- //! @}
-
- #endif /* __utl_meta_selection_h__ */
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