birds.pl

% Run the program by running      go.

go :- hypothesize(Bird),
       write('I guess that the bird is: '), 
       write(Bird), nl, undo.

 /* hypotheses to be tested */ 
hypothesize(chicken) :- chicken, !. 
hypothesize(eagle) :- eagle, !. 
hypothesize(vulture) :- vulture, !. 
hypothesize(turkey) :- turkey, !. 
hypothesize(ostrich) :- ostrich, !. 
hypothesize(penguin) :- penguin, !. 
hypothesize(quail) :- quail, !. 
hypothesize(unknown). /* no diagnosis */

/* animal identification rules */ 
chicken :-  domestic,
                verify(has_comb), 
                verify(domesticated_fowl).
eagle :- fly, not_domestic,
            verify(flies_very_high), 
            verify(sharp_eye_sight).
vulture :- fly, not_domestic,
               verify(scavenger), 
               verify(bald_head). 
turkey :-  domestic,
             verify(large_wattle), 
             verify(use_in_thanksgiving_dinner).
ostrich :-  not_domestic,
               verify(has_long_legs), 
               verify(has_long_neck). 
penguin :- fly, not_domestic, 
                 verify(does_not_fly), 
                 verify(swims), 
                 verify(is_black_and_white). 

quail :-  domestic,
                   verify(small_bird), 
                   verify(white_eye_strip). 
/* classification rules */ 
fly :- verify(flies). 

domestic :- verify(found_at_home). 
not_domestic :- verify(found_in_the_wild). 

/* how to ask questions */ 
ask(Question) :- 
        write('Does the bird have the following attribute: '), 
        write(Question), write('? '), 
         read(Response), nl, 
         ( (Response == yes ; Response == y) 
         -> assert(yes(Question)) ; 
         assert(no(Question)), fail). 
:- dynamic yes/1,no/1. 
/* How to verify something */ 
verify(S) :- (yes(S) -> true ; (no(S) -> fail ; ask(S))). 
/* undo all yes/no assertions */ 
undo :- retract(yes(_)),fail. 
undo :- retract(no(_)),fail. 
undo.