Functional Programming: A PragPub Anthology

Hello, Swift!

Let’s get a feel for Swift with a concrete example. It’s traditional to start with “hello world,” but to demonstrate functional programming, it makes more sense to start with the factorial function.

func fact(n: Int) -> Int {
  if n == 0 {
    return 1
  } else {
    return n * fact(n - 1)
  }
}

let x = fact(10)
println("The factorial of 10 is \(fact(10))")

This code is pretty unsurprising. The only thing that’s at all unusual is that if you look inside the println, you can see that Swift does string interpolation: if you put \ (expression) into a string, then the result of that expression is converted into a string, and inserted into the enclosing string. That’s been common in scripting languages for a long time, but it hasn’t ...