Functional methods for Swift dictionaries

Dictionary+Extensions.swift

extension Dictionary {
    
    func map<T>(tx: Element->T) -> [T] {
        var memory: [T] = []
        for (k, v) in self {
            memory.append(tx(k, v))
        }
        return memory
    }
    
    func reduce<T>(var initial: T, tx: (Key, Value, T) -> T) -> T {
        for (k, v) in self {
            initial = tx(k, v, initial)
        }
        return initial
    }
    
    func filter(pred: Element->Bool) -> Dictionary<Key, Value> {
        var memory = Dictionary<Key, Value>()
        for (k, v) in self {
            if pred(k, v) {
                memory[k] = v
            }
        }
        return memory
    }
    
}