✨ feat: Add isEmpty method.

Author: make-github-pseudonymous-again

src/adt/RedBlackTree.js

@@ -22,6 +22,15 @@ export class RedBlackTree {
 		this.root = null;
 	}
 
+	/**
+	 * Tells whether the tree is empty.
+	 *
+	 * @returns {boolean} true if empty, false otherwise.
+	 */
+	isEmpty() {
+		return this.root === null;
+	}
+
 	/**
 	 * Adds a key to the tree.
 	 *

test/fixtures.js

@@ -0,0 +1,4 @@
+import {increasing as _inc, decreasing as _dec} from '@aureooms/js-compare';
+
+export const increasing = (a, b) => _inc(a, b);
+export const decreasing = (a, b) => _dec(a, b);

test/src/RedBlackTree/isEmpty.js

@@ -0,0 +1,29 @@
+import test from 'ava';
+
+import {range} from '@aureooms/js-itertools';
+
+import {increasing, decreasing} from '../../fixtures.js';
+
+import {RedBlackTree} from '../../../src/index.js';
+
+const macro = (t, compare, items, expected) => {
+	const tree = RedBlackTree.from(compare, items);
+	t.is(tree.isEmpty(), expected);
+};
+
+macro.title = (title, compare, items, _expected) =>
+	`RedBlackTree.from(${compare.name}, ${
+		title || JSON.stringify(items)
+	}).isEmpty()`;
+
+for (const compare of [increasing, decreasing]) {
+	test(macro, compare, [], true);
+	test(macro, compare, [1], false);
+	test(macro, compare, '', true);
+	test(macro, compare, 'ab', false);
+	test(macro, compare, 'abc', false);
+	test('range(0)', macro, compare, range(0), true);
+	test('range(1)', macro, compare, range(1), false);
+	test('range(10)', macro, compare, range(10), false);
+	test('range(10000)', macro, compare, range(10000), false);
+}