Merge pull request #19 from jsr-core/add-repeat

feat(repeat): add `repeat` module

Author: lambdalisue

README.md

@@ -1073,6 +1073,48 @@ const joined = await pipe(
 console.log(joined); // 12345
 ```
 
+### repeat
+
+Returns an finite iterable that repeats through the given iterable.
+
+```ts
+import { repeat } from "@core/iterutil/repeat";
+
+const iter = repeat([1, 2, 3], 2);
+console.log(Array.from(iter)); // [1, 2, 3, 1, 2, 3]
+```
+
+```ts
+import { repeat } from "@core/iterutil/async/repeat";
+
+const iter = repeat([1, 2, 3], 2);
+console.log(await Array.fromAsync(iter)); // [1, 2, 3, 1, 2, 3]
+```
+
+Use `pipe` and `pipe/async` modules for [@core/pipe] package like.
+
+```ts
+import { pipe } from "@core/pipe";
+import { repeat } from "@core/iterutil/pipe/repeat";
+
+const iter = pipe(
+  [1, 2, 3],
+  repeat(2),
+);
+console.log(Array.from(iter)); // [1, 2, 3, 1, 2, 3]
+```
+
+```ts
+import { pipe } from "@core/pipe";
+import { repeat } from "@core/iterutil/pipe/async/repeat";
+
+const iter = pipe(
+  [1, 2, 3],
+  repeat(2),
+);
+console.log(await Array.fromAsync(iter)); // [1, 2, 3, 1, 2, 3]
+```
+
 ### some
 
 Returns true if at least one element in the iterable satisfies the provided

async/mod.ts

@@ -20,6 +20,7 @@ export * from "./nth.ts";
 export * from "./pairwise.ts";
 export * from "./partition.ts";
 export * from "./reduce.ts";
+export * from "./repeat.ts";
 export * from "./some.ts";
 export * from "./take.ts";
 export * from "./take_while.ts";

async/repeat.ts

@@ -0,0 +1,39 @@
+/**
+ * Returns an infinite iterable that repeats through the given iterable.
+ *
+ * Use {@linkcode https://jsr.io/@core/iterutil/doc/async/cycle/~/cycle cycle} to cycle the iterable
+ * Use {@linkcode https://jsr.io/@core/iterutil/doc/repeat/~/repeat repeat} to repeat the iterable synchronously.
+ *
+ * @param iterable The iterable to repeat.
+ * @returns The repeatd iterable.
+ *
+ * @example
+ * ```ts
+ * import { repeat } from "@core/iterutil/async/repeat";
+ *
+ * const iter = repeat([1, 2, 3], 2);
+ * console.log(await Array.fromAsync(iter)); // [1, 2, 3, 1, 2, 3]
+ * ```
+ */
+export function repeat<T>(
+  iterable: Iterable<T> | AsyncIterable<T>,
+  n: number,
+): AsyncIterable<T> {
+  if (n < 0 || !Number.isSafeInteger(n)) {
+    throw new RangeError(
+      `n must be 0 or positive safe integer, but got ${n}.`,
+    );
+  }
+  if (n === 0) {
+    return async function* () {}();
+  }
+  return async function* () {
+    const array = await Array.fromAsync(iterable);
+    if (array.length === 0) {
+      return;
+    }
+    for (let i = 0; i < n; i++) {
+      yield* array;
+    }
+  }();
+}

async/repeat_test.ts

@@ -0,0 +1,69 @@
+import { assertEquals, assertThrows } from "@std/assert";
+import { assertType, type IsExact } from "@std/testing/types";
+import { toAsyncIterable } from "./to_async_iterable.ts";
+import { repeat } from "./repeat.ts";
+
+Deno.test("repeat", async (t) => {
+  await t.step("with async iterable", async (t) => {
+    await t.step("with non empty iterable", async () => {
+      const result = repeat(toAsyncIterable([0, 1, 2]), 2);
+      const expected = [0, 1, 2, 0, 1, 2];
+      assertEquals(await Array.fromAsync(result), expected);
+      assertType<IsExact<typeof result, AsyncIterable<number>>>(true);
+    });
+
+    await t.step("with single value iterable", async () => {
+      const result = repeat(toAsyncIterable([0]), 2);
+      const expected = [0, 0];
+      assertEquals(await Array.fromAsync(result), expected);
+      assertType<IsExact<typeof result, AsyncIterable<number>>>(true);
+    });
+
+    await t.step("with empty iterable", async () => {
+      const result = repeat(toAsyncIterable([] as number[]), 2);
+      const expected: number[] = [];
+      assertEquals(await Array.fromAsync(result), expected);
+      assertType<IsExact<typeof result, AsyncIterable<number>>>(true);
+    });
+  });
+
+  await t.step("with iterable", async (t) => {
+    await t.step("with non empty iterable", async () => {
+      const result = repeat([0, 1, 2], 2);
+      const expected = [0, 1, 2, 0, 1, 2];
+      assertEquals(await Array.fromAsync(result), expected);
+      assertType<IsExact<typeof result, AsyncIterable<number>>>(true);
+    });
+
+    await t.step("with single value iterable", async () => {
+      const result = repeat([0], 2);
+      const expected = [0, 0];
+      assertEquals(await Array.fromAsync(result), expected);
+      assertType<IsExact<typeof result, AsyncIterable<number>>>(true);
+    });
+
+    await t.step("with empty iterable", async () => {
+      const result = repeat([] as number[], 2);
+      const expected: number[] = [];
+      assertEquals(await Array.fromAsync(result), expected);
+      assertType<IsExact<typeof result, AsyncIterable<number>>>(true);
+    });
+  });
+
+  await t.step("with n=0", async () => {
+    const result = repeat([0, 1, 2], 0);
+    const expected: number[] = [];
+    assertEquals(await Array.fromAsync(result), expected);
+    assertType<IsExact<typeof result, AsyncIterable<number>>>(true);
+  });
+
+  await t.step("throws RangeError", async (t) => {
+    await t.step("if the limit is not 0 nor positive safe integer", () => {
+      assertThrows(() => repeat([], NaN), RangeError);
+      assertThrows(() => repeat([], Infinity), RangeError);
+      assertThrows(() => repeat([], -Infinity), RangeError);
+      assertThrows(() => repeat([], -1), RangeError);
+      assertThrows(() => repeat([], 1.1), RangeError);
+    });
+  });
+});

deno.jsonc

@@ -26,6 +26,7 @@
     "./async/pairwise": "./async/pairwise.ts",
     "./async/partition": "./async/partition.ts",
     "./async/reduce": "./async/reduce.ts",
+    "./async/repeat": "./async/repeat.ts",
     "./async/some": "./async/some.ts",
     "./async/take": "./async/take.ts",
     "./async/take-while": "./async/take_while.ts",
@@ -77,6 +78,7 @@
     "./pipe/async/pairwise": "./pipe/async/pairwise.ts",
     "./pipe/async/partition": "./pipe/async/partition.ts",
     "./pipe/async/reduce": "./pipe/async/reduce.ts",
+    "./pipe/async/repeat": "./pipe/async/repeat.ts",
     "./pipe/async/some": "./pipe/async/some.ts",
     "./pipe/async/take": "./pipe/async/take.ts",
     "./pipe/async/take-while": "./pipe/async/take_while.ts",
@@ -103,13 +105,15 @@
     "./pipe/pairwise": "./pipe/pairwise.ts",
     "./pipe/partition": "./pipe/partition.ts",
     "./pipe/reduce": "./pipe/reduce.ts",
+    "./pipe/repeat": "./pipe/repeat.ts",
     "./pipe/some": "./pipe/some.ts",
     "./pipe/take": "./pipe/take.ts",
     "./pipe/take-while": "./pipe/take_while.ts",
     "./pipe/uniq": "./pipe/uniq.ts",
     "./pipe/zip": "./pipe/zip.ts",
     "./range": "./range.ts",
     "./reduce": "./reduce.ts",
+    "./repeat": "./repeat.ts",
     "./some": "./some.ts",
     "./take": "./take.ts",
     "./take-while": "./take_while.ts",
@@ -156,6 +160,7 @@
     "@core/iterutil/async/pairwise": "./async/pairwise.ts",
     "@core/iterutil/async/partition": "./async/partition.ts",
     "@core/iterutil/async/reduce": "./async/reduce.ts",
+    "@core/iterutil/async/repeat": "./async/repeat.ts",
     "@core/iterutil/async/some": "./async/some.ts",
     "@core/iterutil/async/take": "./async/take.ts",
     "@core/iterutil/async/take-while": "./async/take_while.ts",
@@ -209,6 +214,7 @@
     "@core/iterutil/pipe/async/pairwise": "./pipe/async/pairwise.ts",
     "@core/iterutil/pipe/async/partition": "./pipe/async/partition.ts",
     "@core/iterutil/pipe/async/reduce": "./pipe/async/reduce.ts",
+    "@core/iterutil/pipe/async/repeat": "./pipe/async/repeat.ts",
     "@core/iterutil/pipe/async/some": "./pipe/async/some.ts",
     "@core/iterutil/pipe/async/take": "./pipe/async/take.ts",
     "@core/iterutil/pipe/async/take-while": "./pipe/async/take_while.ts",
@@ -237,13 +243,15 @@
     "@core/iterutil/pipe/pairwise": "./pipe/pairwise.ts",
     "@core/iterutil/pipe/partition": "./pipe/partition.ts",
     "@core/iterutil/pipe/reduce": "./pipe/reduce.ts",
+    "@core/iterutil/pipe/repeat": "./pipe/repeat.ts",
     "@core/iterutil/pipe/some": "./pipe/some.ts",
     "@core/iterutil/pipe/take": "./pipe/take.ts",
     "@core/iterutil/pipe/take-while": "./pipe/take_while.ts",
     "@core/iterutil/pipe/uniq": "./pipe/uniq.ts",
     "@core/iterutil/pipe/zip": "./pipe/zip.ts",
     "@core/iterutil/range": "./range.ts",
     "@core/iterutil/reduce": "./reduce.ts",
+    "@core/iterutil/repeat": "./repeat.ts",
     "@core/iterutil/some": "./some.ts",
     "@core/iterutil/take": "./take.ts",
     "@core/iterutil/take-while": "./take_while.ts",

mod.ts

@@ -22,6 +22,7 @@ export * from "./pairwise.ts";
 export * from "./partition.ts";
 export * from "./range.ts";
 export * from "./reduce.ts";
+export * from "./repeat.ts";
 export * from "./some.ts";
 export * from "./take.ts";
 export * from "./take_while.ts";

pipe/async/mod.ts

@@ -19,6 +19,7 @@ export * from "./nth.ts";
 export * from "./pairwise.ts";
 export * from "./partition.ts";
 export * from "./reduce.ts";
+export * from "./repeat.ts";
 export * from "./some.ts";
 export * from "./take.ts";
 export * from "./take_while.ts";

pipe/async/repeat.ts

@@ -0,0 +1,24 @@
+import { repeat as base } from "@core/iterutil/async/repeat";
+
+/**
+ * An operator to return a function that repeats the elements of an iterable.
+ *
+ * See {@linkcode https://jsr.io/@core/iterutil/doc/async/repeat/~/repeat repeat} for native repeat.
+ *
+ * @example
+ * ```ts
+ * import { pipe } from "@core/pipe";
+ * import { repeat } from "@core/iterutil/pipe/async/repeat";
+ *
+ * const iter = pipe(
+ *   [1, 2, 3],
+ *   repeat(2),
+ * );
+ * console.log(await Array.fromAsync(iter)); // [1, 2, 3, 1, 2, 3]
+ * ```
+ */
+export function repeat<T>(
+  n: number,
+): (iterable: Iterable<T> | AsyncIterable<T>) => AsyncIterable<T> {
+  return (iterable: Iterable<T> | AsyncIterable<T>) => base(iterable, n);
+}

pipe/async/repeat_test.ts

@@ -0,0 +1,13 @@
+import { assertEquals } from "@std/assert";
+import { assertType, type IsExact } from "@std/testing/types";
+import { pipe } from "@core/pipe";
+import { repeat } from "./repeat.ts";
+
+Deno.test("repeat", async (t) => {
+  await t.step("usage", async () => {
+    const result = pipe([0, 1, 2], repeat(2));
+    const expected = [0, 1, 2, 0, 1, 2];
+    assertEquals(await Array.fromAsync(result), expected);
+    assertType<IsExact<typeof result, AsyncIterable<number>>>(true);
+  });
+});

pipe/mod.ts

@@ -19,6 +19,7 @@ export * from "./nth.ts";
 export * from "./pairwise.ts";
 export * from "./partition.ts";
 export * from "./reduce.ts";
+export * from "./repeat.ts";
 export * from "./some.ts";
 export * from "./take.ts";
 export * from "./take_while.ts";