Reorganized repo using yarn and workspaces

packages/common/src/iterators.ts

@@ -0,0 +1,62 @@
+export function* map<T, U>(iter: IterableIterator<T>, fn: (item: T) => U): IterableIterator<U> {
+    for (const item of iter) {
+        yield fn(item);
+    }
+}
+
+export function* chain<T>(a: IterableIterator<T>, b: IterableIterator<T>): IterableIterator<T> {
+    yield* a;
+    yield* b;
+}
+
+export function* zip<T, U>(a: IterableIterator<T>, b: IterableIterator<U>): IterableIterator<[T, U]> {
+    let itemA = a.next();
+    let itemB = b.next();
+
+    while (!itemA.done && !itemB.done) {
+        yield [itemA.value, itemB.value];
+
+        itemA = a.next();
+        itemB = b.next();
+    }
+}
+
+export function* take<T>(iter: IterableIterator<T>, n: number): IterableIterator<T> {
+    for (const item of iter) {
+        if (n-- === 0) {
+            return;
+        }
+
+        yield item;
+    }
+}
+
+export function skip<T>(iter: IterableIterator<T>, n: number): IterableIterator<T> {
+    while (n-- !== 0 && !iter.next().done) {}
+
+    return iter;
+}
+
+export function reduce<T, R>(iter: IterableIterator<T>, fn: (accu: R, item: T) => R, accumulator: R): R {
+    for (const item of iter) {
+        accumulator = fn(accumulator, item);
+    }
+
+    return accumulator;
+}
+
+export function join(iter: IterableIterator<{ toString: () => string }>, glue: string): string {
+    const first = iter.next();
+
+    if (first.done) {
+        return '';
+    }
+
+    let result = first.value.toString();
+
+    for (const item of iter) {
+        result += glue + item;
+    }
+
+    return result;
+}