✨ feat: First draft for isPartition.

Author: make-github-pseudonymous-again

package.json

@@ -77,6 +77,7 @@
   },
   "dependencies": {},
   "devDependencies": {
+    "@aureooms/js-itertools": "^4.1.0",
     "@babel/cli": "7.11.6",
     "@babel/core": "7.11.6",
     "@babel/preset-env": "7.11.5",
@@ -101,7 +102,11 @@
     "lib"
   ],
   "homepage": "https://aureooms.github.io/js-set-partition",
-  "keywords": ["choose", "partition", "set"],
+  "keywords": [
+    "choose",
+    "partition",
+    "set"
+  ],
   "license": "AGPL-3.0",
   "main": "lib/index.js",
   "prettier": {

src/index.js

@@ -0,0 +1,8 @@
+import isPartition from './isPartition';
+
+/* eslint import/no-anonymous-default-export: [2, {"allowObject": true}] */
+export default {
+	isPartition,
+};
+
+export {isPartition};

src/isPartition.js

@@ -0,0 +1,18 @@
+const isPartition = (elements, partition) => {
+	const notyetseen = new Set(elements);
+
+	for (const part of partition) {
+		let partIsEmptySet = true;
+		for (const element of part) {
+			partIsEmptySet = false;
+			if (notyetseen.has(element)) notyetseen.delete(element);
+			else return false;
+		}
+
+		if (partIsEmptySet) return false;
+	}
+
+	return notyetseen.size === 0;
+};
+
+export default isPartition;

test/src/isPartition.js

@@ -0,0 +1,35 @@
+import test from 'ava';
+
+import {iter, range, list, map} from '@aureooms/js-itertools';
+
+import {isPartition} from '../../src';
+
+const macro = (t, n, partition, is) => {
+	t.is(isPartition(range(n), partition), is, 'partition');
+	t.is(isPartition(range(n), map(iter, partition)), is, 'map(iter, partition)');
+	t.is(
+		isPartition(range(n), list(map(iter, partition))),
+		is,
+		'list(map(iter, partition))',
+	);
+	t.is(
+		isPartition(range(n), list(map((x) => x, partition))),
+		is,
+		'list(map(x => x, partition))',
+	);
+};
+
+macro.title = (title, n, partition, is) =>
+	`isPartition(${n}, ${JSON.stringify(partition)} = ${is})`;
+
+test(macro, 5, [[0, 1, 2, 3, 4]], true);
+test(macro, 5, [[0], [1], [2], [3], [4]], true);
+test(macro, 5, [[0, 1], [2], [3], [4]], true);
+test(macro, 5, [[2, 1], [3], [0, 4]], true);
+
+test(macro, 5, [[], [0], [1], [2], [3], [4]], false);
+test(macro, 5, [[0], [0], [1], [2], [3], [4]], false);
+test(macro, 5, [[5], [0], [1], [2], [3], [4]], false);
+test(macro, 5, [[-1], [0], [1], [2], [3], [4]], false);
+test(macro, 5, [[2 ** 53 - 1], [0], [1], [2], [3], [4]], false);
+test(macro, 5, [[-(2 ** 53)], [0], [1], [2], [3], [4]], false);