lazy-range.js

// So this is fking incredible. Its actually possible to
// do totally immutable state inside a generator.
// No mutations.  No 'let's.  No shame!
function* range(start, end, step = 1, current = start) {
    yield current;
    if (current < end) yield* range(start, end, step, current + step);
}

// In the name of the Turing, and of the Crockford, and of the holy Atwood, Amen.
console.log(...range(5, 15));
// => 5 6 7 8 9 10 11 12 13 14 15
console.log(...range(5, 15, 2));
// => 5 7 9 11 13 15