Share utility functions from Timetable

Move the genereic pairs, enumerate and setEquals functions from
Timetable to shared/utils/functions to make them available for reuse.

shared/utils/functions.ts

@@ -0,0 +1,43 @@
+/** Returns a tuple consisting of a running index starting from 0, and the item of the iterable */
+export function* enumerate<T>(iterable: Iterable<T>) {
+	let index = 0;
+	for (const item of iterable) {
+		yield [index++, item] as [number, T];
+	}
+}
+
+/** Returns adjacent pairs from iterable */
+export function* pairs<T>(iterable: Iterable<T>) {
+	let first;
+	let second;
+	for (const [index, item] of enumerate(iterable)) {
+		[first, second] = [second, item];
+		if (index >= 1) {
+			yield [first, second] as [T, T];
+		}
+	}
+}
+
+/**
+	Returns true if all sets are equal
+	@param sets set to compare
+	@returns true if all sets are the same size and have the same elements
+*/
+export function setEquals<T>(...sets: Set<T>[]) {
+	if (sets.length < 2) {
+		throw TypeError("At least two sets must be passed to setEquals");
+	}
+	const ref = sets[0];
+	const rest = sets.slice(1);
+	if (rest.some(set => set.size !== ref.size)) {
+		return false;
+	}
+	for (const set of rest) {
+		for (const el of set) {
+			if (!ref.has(el)) {
+				return false;
+			}
+		}
+	}
+	return true;
+}