Swift Unless/When

Swift Unless_When.swift

// Basically, these are if and else statements respectively
// without the opposite clause

func when(test: @autoclosure () -> Bool, action: () -> ()) {
    if test() { action() }
}

func unless(test: @autoclosure () -> Bool, action: () -> ()) {
    if !test() { action() }
}

// Examples

when(3 == 5){
    println("three equals five")         // Will print!
}

unless(3 == 5){
    println("three does not equal five") // Will never print.
}

when(1 == 1){
    println("one equals one")            // Will print!
}

unless(1 == 1){
    println("one does not equal one")    // Will never print.
}

be aware https://airspeedvelocity.net/2014/06/28/extending-the-swift-language-is-cool-but-be-careful/