Re: Lisp newbie needs help

B. Pym wrote:

(defun my-test ()
   (loop for number = (1+ (random 6))
         as sum = number then (+ sum number)
         until (= number 1)
         do (format t "~&~D thrown. Sum: ~D" number sum)
         finally (format t "~&One thrown.")))

 
Gauche Scheme
 
(use srfi-1)  ;; unfold
(use srfi-27) ;; random-integer
 
(define (my-test)
  (fold
    (^(n sum) (print n " thrown.  Sum: " (inc! sum n)) sum)
    0
    (cdr (unfold zero? ($ + 1 $) (^_ (random-integer 6)) -1)))
  (print "One thrown."))
 
 
gosh> (my-test)
2 thrown.  Sum: 2
2 thrown.  Sum: 4
6 thrown.  Sum: 10
One thrown.
 
gosh> (my-test)
One thrown.
 
 
Explanation of "unfold":
 
Function: unfold end-test key gen-next-seed seed :optional tail-gen
 
(unfold zero? (lambda(n) (+ 800 n)) (lambda(n) (- n 1)) 7)
  ===>
(807 806 805 804 803 802 801)
 
(unfold zero? (lambda(n) (+ 800 n)) (lambda(n) (- n 1)) 7
  (lambda(n) (list "The number" n "ended the unfolding.")))
  ===>
(807 806 805 804 803 802 801 "The number" 0 "ended the unfolding.")

Using "do" is a bit tricky, but the result is shorter.

(define (my-test)
  (do ((n #f (+ 1 (random-integer 6)))
       (sum 0))
    ((eqv? 1 n) (print "One thrown."))
    (if n (print n " thrown.  Sum: " (inc! sum n)))))