export interface Curried<A, B, T> {
  (a: A): (b: B) => T;
  (a: A, b: B): T;
}

export function curry2<A, B, T>(fn: (a: A, b: B) => T): Curried<A, B, T> {
  function curried(a: A): (b: B) => T;
  function curried(a: A, b: B): T;
  function curried(a: A, ...b: [] | [B]): T | ((b: B) => T) {
    if (b.length === 0) {
      return b => fn(a, b);
    } else {
      return fn(a, ...b);
    }
  }
  return curried;
}