Implementing a counter as a function

counter-function.swift

// Impelentation Counter as a Function

typealias Mutators = () -> ()
typealias Getter = () -> Int
typealias Setter = (Int) -> ()

func Counter(number initial: Int) -> (getNumber: Getter, setNumber: Setter, increment: Mutators, decrement: Mutators) {
  var v = initial
  
  let getNumber = { return v }
  let setNumber = { v = $0 }
  let increment = { v += 1 }
  let decrement = { v -= 1 }
  
  return (
    getNumber: getNumber,
    setNumber: setNumber,
    increment: increment,
    decrement: decrement)
}

let c = Counter(number: 1)
print(c.getNumber())
c.increment()
print(c.getNumber())
c.decrement()
print(c.getNumber())
c.setNumber(20)
print(c.getNumber())