Dinamyc programming.swift

gistfile1.swift

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

let factorial = memoize { factorial, x in x == 0 ? 1 : x * factorial(x - 1) }