sicp-ex-4.62



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meteorgan

  
  
 rule: 
 (assert! (rule (last-pair (?x) (?x)))) 
 (assert! (rule (last-pair (?u . ?v) (?x)) 
                (last-pair ?v (?x)))) 
  
 ;;; Query input: 
 (last-pair (3) ?x) 
  
 ;;; Query output: 
 (last-pair (3) (3)) 
 ;;; Query input: 
 (last-pair (1 2 3) ?x) 
  
 ;;; Query output: 
 (last-pair (1 2 3) (3)) 
 ;;; Query input: 
 (last-pair (2 ?x) (3)) 
  
 ;;; Query output: 
 (last-pair (2 3) (3)) 
  
 there is no answer for (last-pair ?x (3))