question: fromTo

README.md

@@ -113,6 +113,7 @@ I started this in the [issue #176](https://buttondown.email/cassidoo/archive/we-
 - [334 - letters](src/2024/334-letters)
 - [335 - flip](src/2024/335-flip)
 - [337 - daysBetween](src/2024/337-daysBetween)
+- [339 - fromTo](src/2024/339-fromTo)
 </details>
 
 ## Installing & Running

src/2024/339-fromTo/README.md

@@ -0,0 +1,26 @@
+# fromTo
+
+Interview question of the [issue #339 of rendezvous with cassidoo](https://buttondown.email/cassidoo/archive/youve-got-to-love-whats-yours-alicia-keys/).
+
+## The Question
+
+**Write a function that produces a generator that produces values in a range.**
+
+Example:
+
+```js
+let range = fromTo(0,3)
+
+> range()
+0
+> range()
+1
+> range()
+2
+> range()
+null
+```
+
+## Installing & Running
+
+Just `pnpm i` to install all dependencies and then `pnpm t` to run the tests!

src/2024/339-fromTo/fromTo.test.ts

@@ -0,0 +1,35 @@
+import { getDirection, fromTo } from './fromTo';
+
+describe('#getDirection', () => {
+	it('should positive direction', () => {
+		expect(getDirection(0, 3)).toBe(1);
+		expect(getDirection(0, 0)).toBe(1);
+	});
+
+	it('should negative direction', () => {
+		expect(getDirection(3, 0)).toBe(-1);
+	});
+});
+
+describe('#fromTo', () => {
+	it('should generate values in the specified range', () => {
+		const range = fromTo(0, 3);
+		expect(range()).toBe(0);
+		expect(range()).toBe(1);
+		expect(range()).toBe(2);
+		expect(range()).toBeNull();
+	});
+
+	it('should generate values in single-step range', () => {
+		const range = fromTo(0, 0);
+		expect(range()).toBeNull();
+	});
+
+	it('should generate values in an inverse range', () => {
+		const range = fromTo(3, 0);
+		expect(range()).toBe(3);
+		expect(range()).toBe(2);
+		expect(range()).toBe(1);
+		expect(range()).toBeNull();
+	});
+});

src/2024/339-fromTo/fromTo.ts

@@ -0,0 +1,30 @@
+/*
+Write a function that produces a generator that produces values in a range.
+
+Example:
+
+let range = fromTo(0,3)
+
+> range()
+0
+> range()
+1
+> range()
+2
+> range()
+null
+*/
+
+export function getDirection(from: number, to: number) {
+	return (-1) ** Number(from > to);
+}
+
+export function fromTo(from: number, to: number): () => number | null {
+	const direction = getDirection(from, to);
+	from -= direction;
+
+	return () => {
+		from += direction;
+		return from === to ? null : from;
+	};
+}