sum(1)(2)(3) Variations and Follow-Up Questions

sum(1)(2)(3) Variations and Follow-Up Questions

Variation 1: sum(1)(2)(3)() - Empty Call Termination

function sum(a) {
  return function (b) {
    if (b !== undefined) return sum(a + b);
    return a;
  };
}

Variation 2: sum(1)(2)(3) + 0 - toString

function sum(n) {
  const fn = (m) => sum(n + m);
  fn.toString = () => n;
  return fn;
}

Variation 3: sum(1, 2)(3)(4) - Mixed Arguments

function sum(...args) {
  const total = args.reduce((a, b) => a + b, 0);
  return function (b) {
    if (b !== undefined) return sum(total + b);
    return total;
  };
}

Follow-Up Questions

1. "How would you support sum(1, 2)(3)?" - use rest params to accept multiple args.
2. "How would you add multiplication?" - create a similar multiply function.
3. "What if the chain is infinite?" - it already is; it only terminates when you call with no arg.
4. "How would you convert this to a generic curry?" - use the generic curry function.

The Takeaway

Variations: empty call termination (if b !== undefined), toString (type coercion), mixed arguments (rest params). Follow-ups: support multiple args, add other operations, generic curry. Practice each variation.