🚧 progress: Import existing sources, tests, and code samples.

Author: make-github-pseudonymous-again

README.md

@@ -4,13 +4,16 @@
 Iterable round-robin for JavaScript.
 See [docs](https://iterable-iterator.github.io/round-robin/index.html).
 
-> :building_construction: Caveat emptor! This is work in progress. Code may be
-> working. Documentation may be present. Coherence may be. Maybe.
-
 > :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).
 
+
+```js
+import {roundRobin} from '@iterable-iterator/round-robin';
+roundRobin( [ "ABC" , "D" , "EF" ] ) ; // A D E B F C
+```
+
 [![License](https://img.shields.io/github/license/iterable-iterator/round-robin.svg)](https://raw.githubusercontent.com/iterable-iterator/round-robin/main/LICENSE)
 [![Version](https://img.shields.io/npm/v/@iterable-iterator/round-robin.svg)](https://www.npmjs.org/package/@iterable-iterator/round-robin)
 [![Tests](https://img.shields.io/github/workflow/status/iterable-iterator/round-robin/ci:test?event=push&label=tests)](https://github.com/iterable-iterator/round-robin/actions/workflows/ci:test.yml?query=branch:main)

package.json

@@ -59,12 +59,19 @@
     "release": "np --message ':hatching_chick: release: Bumping to v%s.'",
     "test": "ava"
   },
-  "dependencies": {},
+  "dependencies": {
+    "@functional-abstraction/operator": "^1.0.4",
+    "@iterable-iterator/cycle": "^0.0.1",
+    "@iterable-iterator/iter": "^0.0.2",
+    "@iterable-iterator/map": "^0.0.1",
+    "@iterable-iterator/slice": "^0.0.1"
+  },
   "devDependencies": {
     "@babel/core": "7.14.0",
     "@babel/preset-env": "7.14.0",
     "@babel/register": "7.13.16",
     "@commitlint/cli": "12.1.1",
+    "@iterable-iterator/list": "^0.0.2",
     "@js-library/commitlint-config": "0.0.4",
     "ava": "3.15.0",
     "babel-plugin-transform-remove-console": "6.9.4",

src/index.js

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

src/roundRobin.js

@@ -0,0 +1,45 @@
+import {len} from '@functional-abstraction/operator';
+
+import {slice} from '@iterable-iterator/slice';
+import {cycle} from '@iterable-iterator/cycle';
+import {map} from '@iterable-iterator/map';
+import {iter} from '@iterable-iterator/iter';
+
+/**
+ * Yields the first item of the first input iterable, then the first item of
+ * the second input iterable, etc., until the last input iterable. Then start
+ * again with the second item of the first input iterable, etc. If one of the
+ * input iterable is exhausted, it is removed from the list of input iterables
+ * and the algorithm continues until all input iterables have been exhausted.
+ *
+ * @example
+ * // returns ['A','D','E','B','F','C]
+ * list( roundrobin(['ABC', 'D', 'EF']) )
+ *
+ * @param {Iterable[]} iterables - The input iterables.
+ * @returns {IterableIterator}
+ *
+ */
+export default function* roundRobin(iterables) {
+	let pending = len(iterables);
+
+	let iterators = cycle(map(iter, iterables));
+
+	while (pending) {
+		while (true) {
+			const iterator = iterators.next().value;
+
+			const it = iterator.next();
+
+			if (it.done) {
+				break;
+			}
+
+			yield it.value;
+		}
+
+		--pending;
+
+		iterators = cycle(slice(iterators, 0, pending, 1));
+	}
+}

test/src/api.js

@@ -0,0 +1,15 @@
+import test from 'ava';
+
+import {list} from '@iterable-iterator/list';
+import {roundRobin} from '../../src/index.js';
+
+const repr = (x) => JSON.stringify(x);
+
+const macro = (t, iterables, expected) => {
+	t.deepEqual(list(roundRobin(iterables)), expected);
+};
+
+macro.title = (title, iterables, expected) =>
+	title ?? `roundRobin(${repr(iterables)}) is ${repr(expected)}`;
+
+test(macro, ['ABC', 'D', 'EF'], ['A', 'D', 'E', 'B', 'F', 'C']);