close #137: add array diff function

src/data/array/index.ts

@@ -216,3 +216,13 @@ export const find = <A>(list: A[], cb: FindFunc<A>): Maybe<A> => {
  */
 export const isEqual = <A>(list1: A[], list2: A[]): boolean =>
     list1.every((val, idx) => list2[idx] === val);
+
+/**
+ * diff returns a simple difference between two arrays.
+ *
+ * Comparison is done via contains()
+ */
+export const diff = <A>(list1: A[], list2: A[]): A[] =>
+    [...list1, ...list2].filter(
+        value => !contains(list1, value) || !contains(list2, value)
+    );

test/data/array_test.ts

@@ -18,7 +18,8 @@ import {
     flatten,
     concat,
     find,
-    isEqual
+    isEqual,
+    diff
 } from '../../src/data/array';
 
 describe('array', () => {
@@ -267,4 +268,18 @@ describe('array', () => {
             assert(isEqual([1, 2, 3], [1, 3, 2])).false();
         });
     });
+
+    describe('diff', () => {
+        it('should produce the diff elements ', () => {
+            assert(diff([1, 2, 3], [2, 3, 4])).equate([1, 4]);
+        });
+
+        it('should work with empty arrays ', () => {
+            assert(diff([1, 2, 3], [])).equate([1, 2, 3]);
+
+            assert(diff([], [2, 3, 4])).equate([2, 3, 4]);
+
+            assert(diff([], [])).equate([]);
+        });
+    });
 });