type Port {
  value: Int >= 1 and <= 65535
}

type Rate {
  value: Decimal >= 0.0 and <= 1.0
}

type Row { value: Int }

choose(value: Int >= 1 and <= 65535) (answer: Port) pure {
  answer = Port { value = value }
}
choose(value: other) (answer: Port) pure {
  answer = Port { value = 8080 }
}

step(value: Port) (answer: Int >= 2 and <= 65536) pure {
  answer = value.value + 1
}

scaled(value: Rate) (answer: Decimal >= 0.0 and <= 100.0) pure {
  answer = value.value * 100.0
}

total(values: List<Port>) (answer: Int) pure {
  answer = sum(step, values)
}

rates(values: List<Rate>) (answer: Decimal) pure {
  answer = sum(scaled, values)
}

apply(route: handler(value: Int >= 1) (answer: Int >= 2)) (answer: Int >= 2) {
  answer = route(1)
}

constant(value: Int) (answer: Int) pure { answer = 2 }

snapshot() (answer: Int >= 1) pure {
  original = Row { value = 3 }
  saved = original
  original.value = 0
  answer = saved.value
}

verify() (answer: Bool) {
  answer = choose(0).value == 8080 and step(choose(65535)) == 65536 and total([choose(1), choose(2)]) == 5 and rates([Rate { value = 0.25 }, Rate { value = 0.5 }]) == 75.0 and snapshot() == 3 and apply(constant) == 2
}