sicp-ex-4.42

  
  
 (define (lier) 
   (let ((a (amb 1 2 3 4 5)) 
         (b (amb 1 2 3 4 5)) 
         (c (amb 1 2 3 4 5)) 
         (d (amb 1 2 3 4 5)) 
         (e (amb 1 2 3 4 5))) 
     (require (or (and (= d 2) (not (= a 3))) (and (not (= d 2)) (= a 3)))) 
     (require (or (and (= b 1) (not (= c 2))) (and (not (= b 1)) (= c 2)))) 
     (require (or (and (= c 3) (not (= b 5))) (and (not (= c 3)) (= b 5)))) 
     (require (or (and (= d 2) (not (= e 4))) (and (not (= d 2)) (= e 4)))) 
     (require (or (and (= e 4) (not (= a 1))) (and (not (= e 4)) (= a 1)))) 
     (require (distinct? (list a b c d e))) 
     (list a b c d e))) 
 result is: (3 5 2 1 4)