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% https://raw.githubusercontent.com/Anniepoo/prolog-examples/master/birds.pl
% renamed birds.pro to test pro disambiguation
:- module(birds, [solve/0]).
%
% Start of an implementation of the code at
% http://www.amzi.com/ExpertSystemsInProlog/
%
%
:- dynamic
known/3,
voice/1,
season/1,
cheek/1,
head/1,
flight/1,
bill/1,
live/1,
nostrils/1.
:- discontiguous bird/1, wings/1.
:- set_prolog_flag(unknown, error).
bird(laysan_albatross):-
family(albatross),
color(white).
bird(black_footed_albatross):-
family(albatross),
color(dark).
bird(whistling_swan) :-
family(swan),
voice(muffled_musical_whistle).
bird(trumpeter_swan) :-
family(swan),
voice(loud_trumpeting).
order(tubenose) :-
nostrils(external_tubular),
live(at_sea),
bill(hooked).
order(waterfowl) :-
feet(webbed),
bill(flat).
family(albatross) :-
order(tubenose),
size(large),
wings(long_narrow).
family(swan) :-
order(waterfowl),
neck(long),
color(white),
flight(ponderous).
bird(canada_goose):-
family(goose),
season(winter),
country(united_states),
head(black),
cheek(white).
bird(canada_goose):-
family(goose),
season(summer),
country(canada),
head(black),
cheek(white).
country(united_states):- region(mid_west).
country(united_states):- region(south_west).
country(united_states):- region(north_west).
country(united_states):- region(mid_atlantic).
country(canada):- province(ontario).
country(canada):- province(quebec).
region(new_england):-
state(X),
member(X, [massachusetts, vermont]).
region(south_east):-
state(X),
member(X, [florida, mississippi]).
state(X) :- member(X, [florida, mississippi, massachusetts, vermont]).
province(X) :- member(X, [ontario, quebec]).
ask(A, V):-
known(yes, A, V), % succeed if true
!. % stop looking
ask(A, V):-
known(_, A, V), % fail if false
!, fail.
% known is barfing
ask(A, V):-
write(A:V), % ask user
write('? : '),
read(Y), % get the answer
asserta(known(Y, A, V)), % remember it
Y == yes. % succeed or fail
ask(A, V):-
\+ multivalued(A),
known(yes, A, V2),
V \== V2,
!, fail.
eats(X):- ask(eats, X).
feet(X):- ask(feet, X).
wings(X):- ask(wings, X).
neck(X):- ask(neck, X).
color(X):- ask(color, X).
multivalued(voice).
multivalued(feed).
size(X):- menuask(size, X, [large, plump, medium, small]).
flight(X):- menuask(flight, X, [ponderous, agile, flap_glide]).
menuask(A, V, MenuList) :-
write('What is the value for'), write(A), write('?'), nl,
write(MenuList), nl,
read(X),
check_val(X, A, V, MenuList),
asserta( known(yes, A, X) ),
X == V.
check_val(X, _A, _V, MenuList) :-
member(X, MenuList), !.
check_val(X, A, V, MenuList) :-
write(X), write(' is not a legal value, try again.'), nl,
menuask(A, V, MenuList).
top_goal(X) :- bird(X).
solve :-
retractall(known/3),
top_goal(X),
write('The answer is '), write(X), nl.
solve :-
write('No answer found.'), nl.
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