Redefined `Length` in terms of `Apply` and `Fold`

* this function illustrates the use case `Apply` is currently intended for
* moved `Take` and `Nth` into separate files to resolve header resolution conflicts

1 files changed, 7 insertions, 65 deletions

diff --git a/src/list/operation/basic.h b/src/list/operation/basic.h
index d80b347..1f4b043 100644
--- a/src/list/operation/basic.h
+++ b/src/list/operation/basic.h
@@ -1,76 +1,18 @@
 #ifndef TYPEASVALUE_SRC_LIST_OPERATION_BASIC_H_
 #define TYPEASVALUE_SRC_LIST_OPERATION_BASIC_H_
 
-#include "operation/math.h"
 #include "higher/fold.h"
+#include "function/apply.h"
+#include "operation/math.h"
 
 namespace tav {
 
 template <typename Cons>
-class Length {
-	private:
-		template <
-			typename,
-			typename Previous
-		>
-		struct count {
-			typedef Add<Size<1>, Previous> type;
-		};
-
-	public:
-		typedef typename Fold<count, Size<0>, Cons>::type type;
-
-};
-
-template <
-	typename Index,
-	typename Cons
->
-struct Nth {
-	typedef typename Nth<
-		Substract<Index, Size<1>>,
-		Tail<Cons>
-	>::type type;
-};
-
-template <typename Index>
-struct Nth<Index, void> {
-	typedef void type;
-};
-
-template <typename Cons>
-struct Nth<Size<0>, Cons> {
-	typedef Head<Cons> type;
-};
-
-template <
-	typename Count,
-	typename Current
->
-struct Take {
-	typedef Cons<
-		Head<Current>,
-		typename Take<
-			Substract<Count, Size<1>>,
-			Tail<Current>
-		>::type
-	> type;
-};
-
-template <typename Current>
-struct Take<Size<0>, Current> {
-	typedef void type;
-};
-
-template <typename Count>
-struct Take<Count, void> {
-	typedef void type;
-};
-
-template <>
-struct Take<Size<0>, void> {
-	typedef void type;
-};
+using Length = Fold<
+	Apply<Add, Size<1>, _1>::pair_type,
+	Size<0>,
+	Cons
+>;
 
 }