From 6568e836eb47ede406b40e32e29dd148240904f1 Mon Sep 17 00:00:00 2001
From: Gaetano Checinski <Gaetano.Checinski@gmail.com>
Date: Sun, 14 Jun 2015 12:14:18 +0200
Subject: [PATCH] Implemented iterable/zip.

---
 src/iterable/zip.js           | 36 +++++++++++++++++++++++++++++++++
 test/spec/iterable/zipSpec.js | 38 +++++++++++++++++++++++++++++++++++
 2 files changed, 74 insertions(+)
 create mode 100644 src/iterable/zip.js
 create mode 100644 test/spec/iterable/zipSpec.js

diff --git a/src/iterable/zip.js b/src/iterable/zip.js
new file mode 100644
index 0000000..9f6623f
--- /dev/null
+++ b/src/iterable/zip.js
@@ -0,0 +1,36 @@
+/**
+ * Yields groups of elements where the first group contains the first elements
+ * of all the iterators, second contains the second items and etc. until one
+ * of the iterators has been exhausted.
+ *
+ * @this {Iterable<Iterable<T>>}
+ * @ntime O(nm)
+ * @dspace O(m)
+ * @example Basic Usage
+ *
+ * ```javascript
+ * [ [1,2], [4,5], [6,7] ]::zip() // yields [1,4,6], [2,5,7]
+ * ```
+*/
+
+export function * zip () : Iterable<Iterable<T>> {
+    const iterators = [...this].map(
+        (iterable) => iterable[Symbol.iterator]()
+    );
+
+    if ( iterators.length === 0 ) { return; }
+
+    while ( true ) {
+        const zipped = [];
+
+        for ( const iterator of iterators ) {
+            const { value, done } = iterator.next();
+
+            if ( done ) { return; }
+
+            zipped.push(value);
+        }
+
+        yield zipped;
+    }
+};
diff --git a/test/spec/iterable/zipSpec.js b/test/spec/iterable/zipSpec.js
new file mode 100644
index 0000000..b7ec7aa
--- /dev/null
+++ b/test/spec/iterable/zipSpec.js
@@ -0,0 +1,38 @@
+import { zip } from "../../../src/iterable/zip";
+
+function * iter () {
+    let i = 0;
+
+    while ( true ) {
+        yield ++i;
+    }
+}
+
+function * iterIter () {
+    yield iter();
+    yield [4, 5];
+    yield [6, 7];
+}
+
+describe("zip()", function () {
+    const zipped = [
+        [1, 4, 6],
+        [2, 5, 7],
+    ];
+
+    it("should zip empty arrays", function () {
+        const toZip = [[1, 2, 3],[]];
+        [...toZip::zip()].should.deep.equal([]);
+        [...[]::zip()].should.deep.equal([]);
+    });
+
+    it("should zip arrays correctly", function () {
+        const toZip = [ [1, 2, 3], [4, 5], [6, 7] ];
+        [...toZip::zip()].should.deep.equal(zipped);
+    });
+
+    it("should zip iterators correctly", function () {
+        const toZip = iterIter();
+        [...toZip::zip()].should.deep.equal(zipped);
+    });
+});