tuple: add a map function over a tuple

tuple.hpp

@@ -22,6 +22,7 @@
 
 #include <tuple>
 #include <type_traits>
+#include <functional>
 
 
 namespace util::tuple {
@@ -165,6 +166,29 @@ namespace util::tuple {
     };
 
 
+    ///////////////////////////////////////////////////////////////////////////
+    namespace detail {
+        template <typename FuncT, typename ArgT, std::size_t ...Indices>
+        auto
+        convert (std::index_sequence<Indices...>, FuncT &&func, ArgT &&arg)
+        {
+            return std::tuple (std::invoke (func, std::get<Indices> (arg))...);
+        }
+    };
+
+    template <
+        typename FuncT,
+        typename ArgT,
+        typename IndicesV = std::make_index_sequence<
+            std::tuple_size_v<std::decay_t<ArgT>>
+        >
+    >
+    auto convert (FuncT &&func, ArgT &&arg)
+    {
+        return detail::convert (IndicesV{}, func, arg);
+    }
+
+
     ///////////////////////////////////////////////////////////////////////////
     /// do nothing with a set of parameters.
     ///