public apply(action: handler(value: Int) (answer: Int), value: Int) (answer: Int) {
  answer = action(value)
}

public mapValues(values: List<Int>) (answer: List<Int>) {
  answer = each(calc.value.adjust, values)
}

public total(values: List<Int>) (answer: Int) {
  answer = reduce(add, values, 0)
}

add(value: Int, state: Int) (answer: Int) {
  answer = state + calc.value.adjust(value)
}

public verify() (answer: Bool) {
  answer = total([1, 2, 3]) == 9
}