sicp-ex-4.63

  
  
 rules: 
 (assert! (rule (father ?s ?f) 
                (or (son ?f ?s) 
                    (and (son ?w ?s) 
                         (wife ?f ?w))))) 
  
 (assert! (rule (grandson ?g ?s) 
                (and (father ?s ?f) 
                     (father ?f ?g)))) 
  
 ;;; Query input: 
 (grandson Cain ?s) 
  
 ;;; Query output: 
 (grandson Cain Irad) 
 ;;; Query input: 
 (father ?s Lamech) 
  
 ;;; Query output: 
 (father Jubal Lamech) 
 (father Jabal Lamech) 
 ;;; Query input: 
 (grandson Methushael ?s) 
  
 ;;; Query output: 
 (grandson Methushael Jubal) 
 (grandson Methushael Jabal)