Implemented `Map` in terms of `Fold`

* as its name implies this _function_ applies a given _function_ to each element of a _Cons_ structure
* added appropriate test case

3 files changed, 42 insertions, 2 deletions

diff --git a/src/list/operation/basic.h b/src/list/operation/basic.h
index ff0a4d7..364a542 100644
--- a/src/list/operation/basic.h
+++ b/src/list/operation/basic.h
@@ -11,14 +11,15 @@ class Length {
 	private:
 		template <
 			typename,
-			typename Current
+			typename Previous
 		>
 		struct Count {
-			typedef Add<Size<1>, Current> type;
+			typedef Add<Size<1>, Previous> type;
 		};
 
 	public:
 		typedef typename Fold<Count, Size<0>, Cons>::type type;
+
 };
 
 template <
diff --git a/src/list/operation/higher/misc.h b/src/list/operation/higher/misc.h
new file mode 100644
index 0000000..708265a
--- /dev/null
+++ b/src/list/operation/higher/misc.h
@@ -0,0 +1,29 @@
+#ifndef TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_MISC_H_
+#define TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_MISC_H_
+
+#include "fold.h"
+
+namespace tav {
+
+template <
+	template<typename> class Function,
+	typename                 List
+>
+class Map {
+	private:
+		template <
+			typename Current,
+			typename Previous
+		>
+		struct FunctionWrapper {
+			typedef Cons<Function<Current>, Previous> type;
+		};
+
+	public:
+		typedef typename Fold<FunctionWrapper, void, List>::type type;
+
+};
+
+}
+
+#endif  // TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_MISC_H_
diff --git a/test.cc b/test.cc
index e642b3a..6b9dffb 100644
--- a/test.cc
+++ b/test.cc
@@ -3,12 +3,17 @@
 #include "type.h"
 #include "operation/math.h"
 #include "conditional/if.h"
+
 #include "list/cons.h"
 #include "list/list.h"
 #include "list/operation/higher/fold.h"
+#include "list/operation/higher/misc.h"
 
 class TypeAsValueTest : public ::testing::Test { };
 
+template <typename Element>
+using quadruple = tav::Multiply<tav::Int<4>, Element>;
+
 TEST_F(TypeAsValueTest, BasicMath) {
 	// (+ 1 2)
 	EXPECT_EQ(3,  ( tav::Add<tav::Int<1>, tav::Int<2>>::value ));
@@ -89,6 +94,11 @@ TEST_F(TypeAsValueTest, ListFold) {
 	EXPECT_EQ(6, ( tav::Fold<tav::Add, tav::Int<0>, tav::List<tav::Int<1>, tav::Int<2>, tav::Int<3>>::type>::type::value ));
 }
 
+TEST_F(TypeAsValueTest, ListMap) {
+	// (map quadruple (list 1 2 3))
+	EXPECT_TRUE(( std::is_same<tav::List<tav::Int<4>, tav::Int<8>, tav::Int<12>>::type, tav::Map<quadruple, tav::List<tav::Int<1>, tav::Int<2>, tav::Int<3>>::type>::type>::value ));
+}
+
 int main(int argc, char **argv) {
 	testing::InitGoogleTest(&argc, argv);