Add identity function object

2021-12-12 14:15:52 -05:00
parent 09d7a311a5
commit 0be868143d
6 changed files with 241 additions and 0 deletions
@@ -0,0 +1,41 @@
+/*
+Copyright 2021 Glen Joseph Fernandes
+(glenjofe@gmail.com)
+
+Distributed under the Boost Software License, Version 1.0.
+(http://www.boost.org/LICENSE_1_0.txt)
+*/
+#ifndef BOOST_FUNCTIONAL_IDENTITY_HPP
+#define BOOST_FUNCTIONAL_IDENTITY_HPP
+
+#include <boost/config.hpp>
+#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+#include <utility>
+#endif
+
+namespace boost {
+
+struct identity {
+    typedef void is_transparent;
+
+#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+    template<class T>
+    BOOST_CONSTEXPR T&& operator()(T&& value) const BOOST_NOEXCEPT {
+        return std::forward<T>(value);
+    }
+#else
+    template<class T>
+    BOOST_CONSTEXPR const T& operator()(const T& value) const BOOST_NOEXCEPT {
+        return value;
+    }
+
+    template<class T>
+    BOOST_CONSTEXPR T& operator()(T& value) const BOOST_NOEXCEPT {
+        return value;
+    }
+#endif
+};
+
+} // boost
+
+#endif