✨ feat: Add rotateLeft and rotateRight.

Author: make-github-pseudonymous-again

README.md

@@ -4,12 +4,14 @@
 ArrayLike rotation for JavaScript.
 See [docs](https://array-like.github.io/rotate/index.html).
 
-> :building_construction: Caveat emptor! This is work in progress. Code may be
-> working. Documentation may be present. Coherence may be. Maybe.
+```js
+import {range} from '@iterable-iterator/range';
+import {rotateLeft} from '@array-like/rotate';
 
-> :warning: Depending on your environment, the code may require
-> `regeneratorRuntime` to be defined, for instance by importing
-> [regenerator-runtime/runtime](https://www.npmjs.com/package/regenerator-runtime).
+const a = Array.from(range(5));
+rotateLeft(a, 0, 5, 2);
+a; // 2 3 4 0 1
+```
 
 [![License](https://img.shields.io/github/license/array-like/rotate.svg)](https://raw.githubusercontent.com/array-like/rotate/main/LICENSE)
 [![Version](https://img.shields.io/npm/v/@array-like/rotate.svg)](https://www.npmjs.org/package/@array-like/rotate)

doc/manual/usage.md

@@ -1,19 +1,8 @@
 # Usage
 
-> :warning: Depending on your environment, the code may require
-> `regeneratorRuntime` to be defined, for instance by importing
-> [regenerator-runtime/runtime](https://www.npmjs.com/package/regenerator-runtime).
-
-First, require the polyfill at the entry point of your application
-```js
-await import('regenerator-runtime/runtime.js');
-// or
-import 'regenerator-runtime/runtime.js';
-```
-
-Then, import the library where needed
+Import the library where needed
 ```js
-const rotate = await import('@array-like/rotate');
+const {rotateLeft, rotateRight} = await import('@array-like/rotate');
 // or
-import * as rotate from '@array-like/rotate';
+import {rotateLeft, rotateRight} from '@array-like/rotate';
 ```

package.json

@@ -59,8 +59,13 @@
     "release": "np --message ':hatching_chick: release: Bumping to v%s.'",
     "test": "ava"
   },
-  "dependencies": {},
+  "dependencies": {
+    "@array-like/reverse": "^0.0.1"
+  },
   "devDependencies": {
+    "@array-like/alloc": "^0.0.1",
+    "@array-like/copy": "^0.0.1",
+    "@array-like/fill": "^0.0.1",
     "@babel/core": "7.14.8",
     "@babel/preset-env": "7.14.8",
     "@babel/register": "7.14.5",

src/index.js

@@ -1,2 +1,2 @@
-const answer = 42;
-export default answer;
+export {default as rotateLeft} from './rotateLeft.js';
+export {default as rotateRight} from './rotateRight.js';

src/rotateLeft.js

@@ -0,0 +1,15 @@
+import rotateRight from './rotateRight.js';
+
+/**
+ * Rotate array values k places to the left in-place in time O(j-i).
+ *
+ * See http://prakhar.me/articles/the-string-rotation-problem/.
+ *
+ * @param {{[x: number]: any}} a
+ * @param {number} i
+ * @param {number} j
+ * @param {number} k
+ */
+const rotateLeft = (a, i, j, k) => rotateRight(a, i, j, j - i - k);
+
+export default rotateLeft;

src/rotateRight.js

@@ -0,0 +1,22 @@
+import assert from 'assert';
+import {reverse} from '@array-like/reverse';
+
+/**
+ * Rotate array values k places to the right in-place in time O(j-i).
+ *
+ * See http://prakhar.me/articles/the-string-rotation-problem/.
+ *
+ * @param {{[x: number]: any}} a
+ * @param {number} i
+ * @param {number} j
+ * @param {number} k
+ */
+const rotateRight = (a, i, j, k) => {
+	assert(k >= 0);
+	assert(k <= j - i);
+	reverse(a, i, j);
+	reverse(a, i, i + k);
+	reverse(a, i + k, j);
+};
+
+export default rotateRight;

test/src/api.js

@@ -0,0 +1,30 @@
+import test from 'ava';
+
+import {alloc} from '@array-like/alloc';
+import {iota} from '@array-like/fill';
+import {copy} from '@array-like/copy';
+
+import {rotateLeft} from '../../src/index.js';
+
+const macro = (t, n, k) => {
+	const a = alloc(n);
+	iota(a, 0, n, 0);
+
+	const reference = alloc(n);
+	copy(a, 0, n, reference, 0);
+
+	rotateLeft(a, 0, n, k);
+	t.is(a.length, n, 'length did not change');
+
+	const expected = reference.slice(k).concat(reference.slice(0, k));
+	t.deepEqual(a, expected, 'works as expected');
+};
+
+macro.title = (title, n, k) => title ?? `${n} - ${k}`;
+
+test(macro, 1000, 0);
+test(macro, 1000, 1);
+test(macro, 1000, 2);
+test(macro, 1000, 3);
+test(macro, 1000, 500);
+test(macro, 1000, 1000);

test/src/rotateLeft.js

@@ -0,0 +1,30 @@
+import test from 'ava';
+
+import {alloc} from '@array-like/alloc';
+import {iota} from '@array-like/fill';
+import {copy} from '@array-like/copy';
+
+import {rotateRight} from '../../src/index.js';
+
+const macro = (t, n, k) => {
+	const a = alloc(n);
+	iota(a, 0, n, 0);
+
+	const reference = alloc(n);
+	copy(a, 0, n, reference, 0);
+
+	rotateRight(a, 0, n, n - k);
+	t.is(a.length, n, 'length did not change');
+
+	const expected = reference.slice(k).concat(reference.slice(0, k));
+	t.deepEqual(a, expected, 'works as expected');
+};
+
+macro.title = (title, n, k) => title ?? `${n} - ${k}`;
+
+test(macro, 1000, 0);
+test(macro, 1000, 1);
+test(macro, 1000, 2);
+test(macro, 1000, 3);
+test(macro, 1000, 500);
+test(macro, 1000, 1000);