Add reduce

examples/src/pipe.cpp

@@ -1,12 +1,20 @@
 #include <utempl/utils.hpp>
 
+struct Container {
+  float data{};
+};
+
 auto main() -> int {
   using namespace utempl;
-  constexpr TupleLike auto tuple = Tuple{1, 2, 3, 4, 5, 6}
+  constexpr auto value = Tuple{1, 2, 3, 4, 5, 6}
     | Take<5>()
-    | Map([](int arg){return arg + 1;})
+    | Map([](int arg) {return arg + 1;})
     | Map([](int arg) -> float {return arg;})
+    | Map([](float arg) -> Container {return {.data = arg};})
     | Reverse()
-    | Take<3>(); // Lazy evaluate
-  static_assert(tuple == Tuple{6.0f, 5.0f, 4.0f});
+    | Take<3>()
+    | Reduce(0.f, [](auto accumulator, Container arg) -> float {
+      return accumulator + arg.data;
+    }); // Lazy evavalue
+  static_assert(value == 15.0f);
 };

include/utempl/utils.hpp

@@ -389,6 +389,17 @@ inline constexpr auto LeftFold(Tuple&& tuple, T&& init, F&& f) {
   });
 };
 
+template <TupleLike Tuple, typename T, typename F>
+inline constexpr auto Reduce(Tuple&& tuple, T&& init, F&& f) {
+  return LeftFold(std::forward<Tuple>(tuple), std::forward<T>(init), std::forward<F>(f));
+};
+
+template <typename T, typename F>
+inline constexpr auto Reduce(T&& init, F&& f) {
+  return [init = std::forward<T>(init), f = std::forward<F>(f)]<TupleLike Tuple>(Tuple&& tuple){
+    return Reduce(std::forward<Tuple>(tuple), std::move(init), std::move(f));
+  };
+};
 
 
 template <TupleLike Tuple, TupleLike Tuple2>