WillNess

/**
 * Lazy lists represented as Closure  (like plus(1))  that gives
 *     NextElt, NextClosure       on call to   call(Closure, NextElt, NextClosure)    -- remarks and edits by wn
 *                                cf.   unfold :: (b -> (a, b)) -> b -> [a]           -- for my personal readability
 *
 * Copyright 2018, XLOG Technologies GmbH, Switzerland
 * Jekejeke Prolog 1.3.0 (a fast and small prolog interpreter)
 */
 
%% source:

WillNess

-- code from http://stackoverflow.com/a/21427171/849891 by András Kovács
combsOf :: Int -> [a] -> [[a]]
combsOf n _ | n < 1   = [[]]
combsOf n (x:xs)      = combsOf n xs ++ map (x:) (combsOf (n - 1) xs)
combsOf _ _           = []

-- what I meant was this
change :: Int -> [Int] -> [[Int]]
change n xs 
     | n<0 || null xs = []

WillNess

(define (rev lst)
  (if (or (null? lst)
          (null? (cdr lst)))
      lst
      (apply (lambda (x . xs)
               (apply (lambda (y . ys)
                        (cons y (rev (cons x (rev ys)))))
                      (rev xs)))
             lst)))

WillNess

(define (make-letter destination message)
  (define (dispatch x)
    (cond ((eq? x 'get-destination) destination)
          ((eq? x 'get-message) message)
          (else "Invalid option.")))
      dispatch)

(define (make-mailbox address)
  (let ((T '()))
    (define (add-post letter)

WillNess

?- fibs(F), take(F, 20, _).
F = [0, 1, 1, 2, 3, 5, 8, 13, 21|...],
freeze(_G2395, zip_with(plus, [2584, 4181|_G2395], [4181|_G2395], _G2395)).