myMap.swift

import Cocoa

extension Array {
    func myMap<A,B>(items: Array<A>, f:((A) -> B)) -> Array<B> {
        var xs: Array<A> = items
        return xs.count == 0 ? [] : [f(xs.removeAtIndex(0))] + myMap(xs,f)
    }

    func myMap<B>(f:((T) -> B)) -> Array<B> {
        return myMap(self,f)
    }
}


var a = [4,2,4,5].myMap({ $0 + 2 })
a