Functional Snippet #1: Decomposing Arrays
The following snippet decomposes an array into a tuple containing the first element, and the rest of the array. If the array is empty, it returns nil:
extension Array {
var decompose : (head: T, tail: [T])? {
return (count > 0) ? (self[0], Array(self[1..<count])) : nil
}
}
This is very useful when you combine it with if let statements or pattern matching. For example, here is a recursive definition of sum:
func sum(xs: [Int]) -> Int {
if let (head, tail) = xs.decompose {
return head + sum(tail)
} else {
return 0
}
}
You can easily define your own decomposing functions on other types, such as dictionaries or strings.