gistfile1.swift

public func memoize<T: Hashable, U>(f: (T) -> U) -> (T) -> U {
    var memo : [T : U] = [:]
    return { x in
        if let q = memo[x] {
            return q
        }
        let r = f(x)
        memo[x] = r
        return r
    }
}