add iterating over grouped items of iterators

src/lib.ts

@@ -2,7 +2,7 @@
 export type { Arr, ClassOf, Constructible, Function, InstanceOf, KeyOfType, Tail } from "./lib/types.ts";
 
 // functions
-export { all, enumerate, filter, filter_map, it, Iter, map, zip } from "./lib/iter.ts";
+export { all, chunk, enumerate, filter, filter_map, it, Iter, map, window, zip } from "./lib/iter.ts";
 export { log_from, next, split_promise, wait } from "./lib/utils.ts";
 
 // Structures

src/lib/iter.ts

@@ -40,6 +40,33 @@ export function* zip<A, B>(a: Iterable<A>, b: Iterable<B>): Generator<[A, B], vo
 	}
 }
 
+export function* chunk<T>(iter: Iterable<T>, size: number, incomplete = true): Generator<T[], void, void> {
+	let chunk = [] as T[];
+	for (const item of iter) {
+		if (chunk.length === size) {
+			yield chunk;
+			chunk = [];
+		}
+		chunk.push(item);
+	}
+	if (incomplete) yield chunk;
+}
+
+export function* window<T>(iter: Iterable<T>, size: number, incomplete = false): Generator<T[], void, void> {
+	const window = [] as T[];
+	for (const item of iter) {
+		window.push(item);
+		if (window.length > size) window.splice(0, 1);
+		if (incomplete || window.length === size) yield [...window];
+	}
+	if (incomplete) {
+		for (const _ in range(0, window.length)) {
+			window.splice(0, 1);
+			yield [...window];
+		}
+	}
+}
+
 export class Iter<T> {
 	iter;
 	[Symbol.iterator] = () => this.iter[Symbol.iterator]();
@@ -68,7 +95,19 @@ export class Iter<T> {
 		return new Iter(zip(this, other));
 	}
 
+	chunk(size: number, incomplete = true) {
+		return new Iter(chunk(this, size, incomplete));
+	}
+
+	window(size: number, incomplete = false) {
+		return new Iter(window(this, size, incomplete));
+	}
+
 	array() {
+		return [...this];
+	}
+
+	array_it() {
 		// deno-lint-ignore no-explicit-any
 		const result: any = [...this];
 		result.it = () => it(result);
@@ -76,7 +115,7 @@ export class Iter<T> {
 	}
 
 	collect<O>(class_: new (it: Iterable<T>) => O): O {
-		return new class_(this);
+		return new class_(this.iter);
 	}
 
 	all(predicate: (item: T) => boolean) {
@@ -84,7 +123,8 @@ export class Iter<T> {
 	}
 }
 
-Deno.test("iter", async () => {
+Deno.test("test_comon", async () => {
+	const { assertEquals } = await import("https://deno.land/std@0.224.0/assert/assert_equals.ts");
 	const items = it(range(0, 10))
 		.map((e) => e * 3)
 		.enumerate()
@@ -92,7 +132,19 @@ Deno.test("iter", async () => {
 		.zip(range(0, 10))
 		.map(JSON.stringify)
 		.collect(Set<string>);
-
-	const { assertEquals } = await import("https://deno.land/std@0.224.0/assert/assert_equals.ts");
 	assertEquals(items, new Set(["[[1,3],0]", "[[3,9],1]", "[[5,15],2]", "[[7,21],3]", "[[9,27],4]"]));
 });
+
+Deno.test("test_chunk", async () => {
+	const { assertEquals } = await import("https://deno.land/std@0.224.0/assert/assert_equals.ts");
+	const items = it(range(0, 5)).chunk(2).array();
+	assertEquals(items, [[0, 1], [2, 3], [4]]);
+});
+
+Deno.test("test_window", async () => {
+	const { assertEquals } = await import("https://deno.land/std@0.224.0/assert/assert_equals.ts");
+	const items = it(range(0, 5)).window(3).array();
+	assertEquals(items, [[0, 1, 2], [1, 2, 3], [2, 3, 4]]);
+	const items_incomplete = it(range(0, 3)).window(3, true).array();
+	assertEquals(items_incomplete, [[0], [0, 1], [0, 1, 2], [1, 2], [2]]);
+});