Support fmap over a tuple

libs/util/include/psemek/util/fmap.hpp

@@ -3,6 +3,7 @@
 #include <psemek/util/range.hpp>
 
 #include <optional>
+#include <tuple>
 
 namespace psemek::util
 {
@@ -25,6 +26,16 @@ namespace psemek::util
 				else
 					return std::optional<R>();
 			}
+
+			template <typename ... Ts>
+			auto operator()(std::tuple<Ts...> && x)
+			{
+				return [&]<std::size_t ... I>(std::index_sequence<I...>){
+					return std::tuple{
+						f(std::get<I>(x))...
+					};
+				}(std::make_index_sequence<sizeof...(Ts)>{});
+			}
 		};
 
 	}