!compile: Some meta:: rework

2019-01-24 10:43:05 +02:00
parent 19f6991a83
commit 031349a44d
17 changed files with 1343 additions and 132 deletions
@@ -0,0 +1,74 @@
+/*!
+ * \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...>;
+
+   //! @}
+}}
+
+//! @}
+
+#endif /* __utl_meta_selection_h__ */