Fun with Apple’s Swift: Using the @prefix operator to mimic Lisp’s + function

Apple’s latest language Swift provides some nifty behaviors and characteristics. Three things we are loving about Swift so far are:

  1. Awesome OOP features: Structs, Enums, Classes can all have methods, optional binding, type safety
  2. Cool Functional language features: Closures (the shorthand syntax is a delight to use), nested functions and types
  3. Interesting Cocoa binding behaviors, as if the language was written to build beautiful Cocoa apps

We are getting solid feeling of how Swift was designed to create powerful and elegant programs. Experience will tell more down the line.

Here is a fun experiment with prefix operators. We wrote the following two custom global functions to mimic Lisp’s + prefix operator:

@prefix func + (ints: Int[]) -> Int {
    var sum = 0
    for int in ints {
        sum += int
    }
    return sum
}
@prefix func + (strings: String[]) -> String {
    var sum = ""
    for string in strings {
        sum += string
    }
    return sum
}

+[100, 200, 200]
// returns 500

+["comp", "uter"]
// returns "computer"