Moved `Sort` list index deletion into `DeleteNth` function

* as it is commonly required functionality and as such should be provided by this library

3 files changed, 37 insertions, 6 deletions

diff --git a/src/list/operation/delete_nth.h b/src/list/operation/delete_nth.h
new file mode 100644
index 0000000..03df12a
--- /dev/null
+++ b/src/list/operation/delete_nth.h
@@ -0,0 +1,21 @@
+#ifndef TYPEASVALUE_SRC_LIST_OPERATION_DELETE_NTH_H_
+#define TYPEASVALUE_SRC_LIST_OPERATION_DELETE_NTH_H_
+
+#include "list/operation/append.h"
+#include "list/operation/take.h"
+#include "list/operation/drop.h"
+
+namespace tav {
+
+template <
+	typename Index,
+	typename List
+>
+using DeleteNth = Append<
+	typename Take<Index, List>::type,
+	typename Drop<Add<Index, Size<1>>, List>::type
+>;
+
+}
+
+#endif  // TYPEASVALUE_SRC_LIST_OPERATION_DELETE_NTH_H_
diff --git a/src/list/operation/higher/sort.h b/src/list/operation/higher/sort.h
index a707a15..f9146d6 100644
--- a/src/list/operation/higher/sort.h
+++ b/src/list/operation/higher/sort.h
@@ -2,6 +2,7 @@
 #define TYPEASVALUE_SRC_LIST_OPERATION_HIGHER_SORT_H_
 
 #include "list/operation/concatenate.h"
+#include "list/operation/delete_nth.h"
 #include "list/operation/higher/partition.h"
 #include "function/apply.h"
 
@@ -16,14 +17,9 @@ class Sort {
 		using index = Divide<typename Length<Sequence>::type, Size<2>>;
 		using pivot = typename Nth<index, Sequence>::type;
 
-		using sequence_sans_pivot = typename Append<
-			typename Take<index, Sequence>::type,
-			typename Drop<Add<index, Size<1>>, Sequence>::type
-		>::type;
-
 		using partitions = typename Partition<
 			Apply<Comparator, pivot, tav::_0>::template single_type,
-			sequence_sans_pivot
+			typename DeleteNth<index, Sequence>::type
 		>::type;
 
 		using lhs = typename Car<partitions>::type;
diff --git a/test.cc b/test.cc
index 8a5c499..931d8f1 100644
--- a/test.cc
+++ b/test.cc
@@ -19,6 +19,7 @@
 #include "list/generator/make_list.h"
 #include "list/generator/higher/list_tabulate.h"
 #include "list/operation/delete.h"
+#include "list/operation/delete_nth.h"
 
 #include "function/apply.h"
 
@@ -595,6 +596,19 @@ static_assert(
 	"(delete 4 (list 1 2 3)) != (list 1 2 3)"
 );
 
+// list delete nth
+
+static_assert(
+	std::is_same<
+		tav::List<tav::Int<1>, tav::Int<3>>::type,
+		tav::DeleteNth<
+			tav::Size<1>,
+			tav::List<tav::Int<1>, tav::Int<2>, tav::Int<3>>::type
+		>::type
+	>::value,
+	"(delete-nth 1 (list 1 2 3)) != (list 1 3)"
+);
+
 // list partition
 
 static_assert(