tuple/value: add reversing operation

test/tuple/value.cpp

@@ -29,5 +29,13 @@ main (void)
         tap.expect_eq (c, util::tuple::value::zip (a, b), "tuple zipping");
     }
 
+    {
+        std::tuple a (1, 2);
+        auto result = util::tuple::value::reverse (a);
+        std::tuple expected (2, 1);
+
+        tap.expect_eq (result, expected, "tuple reverse");
+    }
+
     return tap.status ();
 }

tuple/value.hpp

@@ -17,6 +17,7 @@
 #ifndef CRUFT_UTIL_TUPLE_VALUE_HPP
 #define CRUFT_UTIL_TUPLE_VALUE_HPP
 
+#include "index.hpp"
 #include "../types.hpp"
 
 #include <cstddef>
@@ -123,6 +124,32 @@ namespace util::tuple::value {
             std::forward<Args> (args)...
         );
     }
+
+
+    ///////////////////////////////////////////////////////////////////////////
+    namespace detail {
+        template <typename TupleT, size_t ...Indices>
+        auto
+        reverse (index::indices<Indices...>, TupleT &&val)
+        {
+            return std::make_tuple (
+                std::get<Indices> (val)...
+            );
+        }
+    };
+
+    //-------------------------------------------------------------------------
+    template <typename TupleT>
+    auto
+    reverse (TupleT &&val)
+    {
+        return detail::reverse (
+            index::make_reverse_t<
+                std::tuple_size_v<std::decay_t<TupleT>>
+            > {},
+            std::forward<TupleT> (val)
+        );
+    }
 }