feat(split): add split function

(cherry picked from commit a758b0f)

Author: djcsdy

index.test.ts

@@ -41,6 +41,7 @@ import {
     scanRight,
     scanRight1,
     slice,
+    split,
     sum,
     tail,
     takeWhile
@@ -332,6 +333,15 @@ interface Error {
     type: "error";
 }
 
+test("split", t => {
+    t.deepEqual(split([2, 1, 3, 4, 5, 6], 2), [
+        [2, 1],
+        [3, 4, 5, 6]
+    ]);
+    t.deepEqual(split([2, 1, 3, 4, 5, 6], 0), [[], [2, 1, 3, 4, 5, 6]]);
+    t.deepEqual(split([2, 1, 3, 4, 5, 6], 10), [[2, 1, 3, 4, 5, 6], []]);
+});
+
 function isSuccess<T>(result: Result<T>): result is Success<T> {
     return result.type === "success";
 }

index.ts

@@ -705,6 +705,21 @@ export function scanRight1Fn<T>(
     return array => scanRight1(array, f);
 }
 
+/** Splits the array at the specified index.
+ *
+ * Returns a tuple where the first element is the first `index` elements of the
+ * array, and the second element is the remaining elements of the array. */
+export function split<T>(array: readonly T[], index: number): [T[], T[]] {
+    return [take(array, index), drop(array, index)];
+}
+
+/** Returns a function that splits an array at the specified index.
+ *
+ * This is the curried form of {@link split}. */
+export function splitFn<T>(index: number): (array: readonly T[]) => [T[], T[]] {
+    return array => split(array, index);
+}
+
 export function partition<T, U extends T>(
     array: ArrayLike<T>,
     predicate: (element: T) => element is U