function curry(fn) {
  return function curried() {
    const args = Array.prototype.slice.call(arguments)
    const done = args.length >= fn.length
    if (done) {
      return fn.apply(this, args)
    } else {
      return function() {
        const args2 = Array.prototype.slice.call(arguments)
        return curried.apply(this, args.concat(args2))
      }
    }
  }
}