params.swift

func add(a: Int, b: Int) -> Int {
  return a + b
}

add(1, 2)

/// -----

func add(#a: Int, #b: Int) -> Int {
  return a + b
}

add(a: 1, b: 2)


/// -----

func add(firstNumber a: Int, secondNumber b: Int) -> Int {
  return a + b
}

add(firstNumber: 1, secondNumber: 2)

/// firstNumber and secondNumber are external parameter names. They are used to specify how the caller should name the input params. Internally a and b are used.