meta: A simple meta functionality added. (Untested)

include/utl/meta/bool.h

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+/*!
+ * \file    bool.h
+ * \brief   Template meta-programming bool integral constant
+ *
+ * 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_bool_h__
+#define __utl_meta_bool_h__
+
+#include <utl/impl/version.h>
+#include <utl/meta/integral.h>
+
+/*!
+ * \ingroup meta
+ * \defgroup bool
+ * boolean constant type support header
+ */
+//! @{
+
+namespace utl {
+
+   //! bool_ type
+   template<bool _v>
+     using bool_ = integral_<bool, _v>;
+
+   //! The type used as a compile-time boolean with true value.
+   typedef bool_<true>  true_;
+
+   //! The type used as a compile-time boolean with false value.
+   typedef bool_<false> false_;
+
+}
+
+//! @}
+#endif /* __utl_meta_bool_h__ */

include/utl/meta/if.h

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+/*!
+ * \file    if.h
+ * \brief   Template meta-programming conditional helpers
+ *
+ * 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_if_h__
+#define __utl_meta_if_h__
+
+#include <utl/impl/version.h>
+
+
+/*!
+ * \ingroup meta
+ * \defgroup if
+ * conditional type support header
+ */
+//! @{
+namespace utl {
+
+   //! if_
+   //! @{
+   template <bool _C, typename _T1, typename _T2>
+   struct if_ {
+      typedef _T1 type;
+   };
+
+   template <typename _T1, typename _T2>
+   struct if_ <false, _T1, _T2> {
+      typedef _T2 type;
+   };
+   //! @}
+
+   //! enable_if
+   //! @{
+   template <bool, typename _Tp = void>
+   struct enable_if { };
+
+   // Partial specialization for true.
+   template<typename _Tp>
+   struct enable_if <true, _Tp> {
+      typedef _Tp type;
+   };
+   //! Alias template for enable_if
+   template<bool _C, typename _Tp = void>
+   using enable_if_t = typename enable_if<_C, _Tp>::type;
+   //! @}
+}
+
+//! @}
+#endif /* __utl_meta_if_h__ */

include/utl/meta/integral.h

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+/*!
+ * \file    integral.h
+ * \brief   Template meta-programming integral constant
+ *
+ * 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_integral_h__
+#define __utl_meta_integral_h__
+
+#include <utl/impl/version.h>
+
+/*!
+ * \ingroup meta
+ * \defgroup integral
+ * integral constand support header
+ */
+//! @{
+
+namespace utl {
+
+   //! integral_constant
+   template <typename _Tp, _Tp _v>
+   struct integral_ {
+      using value_type = _Tp;
+      using type       = integral_<_Tp, _v>;
+
+      constexpr operator value_type() const {
+         return value;
+      }
+      constexpr value_type operator()() const {
+         return value;
+      }
+      static constexpr _Tp value = _v;
+   };
+
+   template<typename _Tp, _Tp _v>
+   constexpr _Tp integral_<_Tp, _v>::value;
+}
+//!@}
+
+#endif /* __utl_meta_integral_h__ */

include/utl/meta/logical.h

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+/*!
+ * \file    logical.h
+ * \brief   Template meta-programming logic operator and type relations.
+ *
+ * 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_logical_h__
+#define __utl_meta_logical_h__
+
+#include <utl/impl/version.h>
+#include <utl/meta/bool.h>
+#include <utl/meta/if.h>
+
+/*!
+ * \ingroup meta
+ * \defgroup logic
+ * logic operator and type relations support header
+ */
+//! @{
+namespace utl {
+
+   //! NOT implementation
+   template<bool C_>
+   struct not_ : bool_<!C_> { };
+
+   //! OR implementation
+   //! @{
+   template<typename...> struct or_;
+
+   template<>
+   struct or_<>
+      : false_ { };
+
+   template<typename _T1>
+   struct or_<_T1>
+      : _T1 { };
+
+   template<typename _T1, typename _T2>
+   struct or_ <_T1, _T2>
+     : if_<_T1::value, _T1, _T2>::type { };
+
+   template<typename _T1, typename _T2, typename _T3, typename... _Tn>
+   struct or_<_T1, _T2, _T3, _Tn...>
+      : if_<_T1::value, _T1, or_<_T2, _T3, _Tn...>>::type { };
+   //! @}
+
+   //! AND implementation
+   //! @{
+   template<typename...> struct and_;
+
+   template<>
+   struct and_<>
+      : true_ { };
+
+   template<typename _T1>
+   struct and_ <_T1>
+      : _T1 { };
+
+   template<typename _T1, typename _T2>
+   struct and_<_T1, _T2>
+      : if_<_T1::value, _T2, _T1>::type { };
+
+   template<typename _T1, typename _T2, typename _T3, typename... _Tn>
+   struct and_<_T1, _T2, _T3, _Tn...>
+      : if_<_T1::value, and_<_T2, _T3, _Tn...>, _T1>::type { };
+   //! @}
+
+   //! same
+   //! @{
+   template<typename _T1, typename _T2>
+   struct same_ : false_ { };
+
+   template<typename _Tp>
+   struct same_ <_Tp, _Tp> : true_ { };
+   //! @}
+
+   //! not same
+   //! @{
+   template<typename _T1, typename _T2>
+   struct not_same_ : true_ { };
+
+   template<typename _Tp>
+   struct not_same_ <_Tp, _Tp> : false_ { };
+   //! @}
+}
+
+#endif /* __utl_meta_logical_h__ */

include/utl/meta/sfinae.h

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+/*!
+ * \file    use.h
+ * \brief   Template meta-programming SFINAE helpers
+ *
+ * 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_use_h__
+#define __utl_meta_use_h__
+
+#include <utl/impl/version.h>
+#include <utl/meta/logical.h>
+
+
+/*!
+ * \ingroup meta
+ * \defgroup use
+ * conditional use support header. This is a SFINAE helper
+ */
+//! @{
+namespace utl {
+
+   //! If same type resolves to _Ret, else to SFINAE
+   //! @{
+   template <typename _Tp1, typename _Tp2, typename _Ret>
+   struct use_if_same_ {
+      using type = enable_if_t <
+                      same_<_Tp1, _Tp2>::value,
+                      _Ret
+                   >;
+   };
+   template <typename _Tp1, typename _Tp2, typename _Ret>
+   using use_if_same_t = typename use_if_same_<_Tp1, _Tp2, _Ret>::type;
+   //! @}
+
+   //! If same type resolves to SFINAE, else to _Ret
+   //! @{
+   template <typename _Tp1, typename _Tp2, typename _Ret>
+   struct discard_if_same_ {
+      using type = enable_if_t <
+                      !same_<_Tp1, _Tp2>::value,
+                      _Ret
+                   >;
+   };
+   template <typename _Tp1, typename _Tp2, typename _Ret>
+   using discard_if_same_t = typename discard_if_same_<_Tp1, _Tp2, _Ret>::type;
+   //! @}
+
+}
+
+//! @}
+#endif /* __utl_meta_use_h__ */

include/utl/meta/void.h

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+/*!
+ * \file    void.h
+ * \brief   Template meta-programming void helpers
+ *
+ * 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_void_h__
+#define __utl_meta_void_h__
+
+#include <utl/impl/version.h>
+#include <utl/meta/bool.h>
+
+/*! \ingroup meta
+ * \defgroup void
+ * void_ support header
+ */
+//! @{
+
+namespace utl {
+
+   /*!
+    * Like boost::mpl we made void_ a complete type to allow it to be
+    * instantiated so that it can be passed in as an object that can be
+    * used to select an overloaded function.
+    */
+   struct void_ {
+      typedef void_ type;
+   };
+
+   template<typename _Tp>
+   struct is_void_
+         : false_ { };
+
+   template<>
+   struct is_void_ <void_>
+      : true_ { };
+
+   template<typename _Tp>
+   struct is_not_void_
+      : true_ { };
+
+   template<>
+   struct is_not_void_<void_>
+      : false_ { };
+
+}
+
+//!@}
+
+#endif /* __utl_meta_void_h__ */

include/utl/meta/void_t.h

@@ -0,0 +1,52 @@
+/*!
+ * \file    void_t.h
+ * \brief   Template meta-programming helpers
+ *
+ * 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_void_t_h__
+#define __utl_meta_void_t_h__
+
+#include <utl/impl/version.h>
+
+//! \ingroup meta
+//! \defgroup void_t
+//! A void_t implementation for utl
+//! @{
+namespace utl {
+
+   /*!
+    * Utility meta-function that maps a sequence of any types to the type void
+    * \note The idea is:
+    *    template <typename ...>
+    *    using void_t = void;
+    *
+    * Until CWG 1558 (a C++14 defect), unused parameters in alias templates were not
+    * guaranteed to ensure SFINAE and could be ignored, so earlier compilers require
+    * a more complex definition of void_t, such as the following implementation
+    * https://en.cppreference.com
+    */
+   template<typename... _Ts>
+   struct void_impl {
+      typedef void type;
+   };
+   //! The actual void_t type alias
+   template<typename... _Ts>
+   using void_t = typename void_impl<_Ts...>::type;
+}
+//! @}
+
+#endif /* __utl_meta_void_t_h__ */