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monad-prototype.js
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51 lines (43 loc) · 1.28 KB
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'use strict';
const validatePoint = (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: ${y}`));
return errors;
};
function Point({ x, y }) {
const errors = validatePoint(x, y);
if (errors.length > 0) {
const cause = new AggregateError(errors, 'Validation');
throw new RangeError('Bad coordinates', { cause });
}
const map = (fn) => {
const coord = fn({ x, y });
return new Point({ x: coord.x, y: coord.y });
};
const chain = (fn) => fn({ x, y });
return { map, chain };
}
Point.of = ({ x, y }) => new Point({ x, y });
function PointTransform(fn) {
const ap = (point) => point.map(fn);
return { ap };
}
function Serialized(data) {
const map = (fn) => fn(data);
const tap = (fn) => {
fn(data);
return { map, tap };
};
return { map, tap };
}
const move = (d) => ({ x, y }) => ({ x: x + d.x, y: y + d.y });
const clone = ({ x, y }) => ({ x, y });
const toString = ({ x, y }) => new Serialized(`(${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);