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monad-single.js
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78 lines (63 loc) · 1.44 KB
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'use strict';
class Point {
#x;
#y;
constructor({ x, y }) {
const errors = Point.validate(x, y);
if (errors.length > 0) {
const cause = new AggregateError(errors, 'Validation');
throw new RangeError('Bad coordinates', { cause });
}
this.#x = x;
this.#y = y;
}
static validate(x, y) {
const errors = [];
if (!Number.isFinite(x)) errors.push(new TypeError(`Invalid x: ${x}`));
if (!Number.isFinite(y)) errors.push(new TypeError(`Invalid y: ${y}`));
return errors;
}
static of({ x, y }) {
return new Point({ x, y });
}
map(fn) {
const coords = { x: this.#x, y: this.#y };
return Point.of(fn(coords));
}
chain(fn) {
const coords = { x: this.#x, y: this.#y };
return fn(coords);
}
}
class PointTransform {
constructor(fn) {
this.fn = fn;
}
ap(point) {
return point.map(this.fn);
}
}
class Serialized {
#data;
constructor(data) {
this.#data = data;
}
map(fn) {
fn(this.#data);
return this;
}
tap(fn) {
fn(this.#data);
return this;
}
}
const move = (d) => ({ x, y }) => ({ x: x + d.x, y: y + d.y });
const clone = ({ x, y }) => ({ x, y });
const toString = ({ x, y }) => new Serialized(`(${x}, ${y})`);
// Usage
const p1 = Point.of({ x: 10, y: 20 });
p1.chain(toString).tap(console.log);
const c0 = p1.map(clone);
const t1 = new PointTransform(move({ x: -5, y: 10 }));
const c1 = t1.ap(c0);
c1.chain(toString).tap(console.log);