Implemented higher order function `fold`

* applies a given _function_ to each _Cons_ starting with a initial value
* added appropriate test case

1 files changed, 28 insertions, 0 deletions

diff --git a/src/list/operation/higher/fold.h b/src/list/operation/higher/fold.h
new file mode 100644
index 0000000..6ad4bd7
--- /dev/null
+++ b/src/list/operation/higher/fold.h
@@ -0,0 +1,28 @@
+#ifndef TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_FOLD_H_
+#define TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_FOLD_H_
+
+namespace tav {
+
+template <
+	template<typename, typename> class Function,
+	typename                           Initial,
+	typename                           Current
+>
+struct Fold {
+	typedef typename Function<
+		Head<Current>,
+		typename Fold<Function, Initial, Tail<Current>>::type
+	>::type type;
+};
+
+template <
+	template<typename, typename> class Function,
+	typename                           Initial
+>
+struct Fold<Function, Initial, void> {
+	typedef Initial type;
+};
+
+}
+
+#endif  // TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_FOLD_H_