min_age(18,'light {*filter*}ic').
min_age(21, 'hard liquor').

student('Pierre', 29).
student('John',   21).
student('Julie',  20).
student('Nancy',  17).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
legal(AName, ADrink) :- student(AName, Sage), drink(ADrink, AType),
min_age(Age, AType), Sage >= Age.

so if I do this:
?- legal('Pierre', 'Whiskey').  % this should print Yes
?- legal('Julie', 'Brandy'). % this should print No

Any help at all would be appreciated

There's nothing wrong with your program, it must be your Prolog.

--
Regards

John Fletcher

is there anything wrong with SWI - prolog? that's what I'm using

       home: http://nexus.carleton.ca/~colin/
 public key: http://nexus.carleton.ca/~colin/pubkey.asc
fingerprint: 1AD0 91ED B77A CC2B 87B1  4E51 012B 4BD2 8DC9 D62C

Colin

I've just tried your program on SWI (Win2k) ...

Welcome to SWI-Prolog (Version 4.0.9)
Copyright (c) 1990-2000 University of Amsterdam.
Copy policy: GPL-2 (see www.gnu.org)

For help, use ?- help(Topic). or ?- apropos(Word).

1 ?- [user].
|: drink('Cola','soft drink').
|: drink('7_up','soft drink').
|: drink('white wine', 'light {*filter*}ic').
|: drink('red wine', 'light {*filter*}ic').
|: drink('Brandy', 'hard liquor').
|: drink('Whiskey', 'hard liquor').
|:
|: min_age(18,'light {*filter*}ic').
|: min_age(21, 'hard liquor').
|:
|: student('Pierre', 29).
|: student('John',   21).
|: student('Julie',  20).
|: student('Nancy',  17).
|:
|: %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|: legal(AName, ADrink) :- student(AName, Sage), drink(ADrink, AType),
|: min_age(Age, AType), Sage >= Age.
|: end_of_file.
% user compiled 0.00 sec, 60,860 bytes

Yes
2 ?- legal('Pierre', 'Whiskey').

Yes
3 ?- legal('Julie', 'Brandy').

No

So I'm at a loss to explain it.

--
Regards

John Fletcher

and it works for me now.

thanks extremely very much!!  this assignment is due in less than 2 hours!

colin

       home: http://www.*-*-*.com/ ~colin/
 public key: http://www.*-*-*.com/ ~colin/pubkey.asc
fingerprint: 1AD0 91ED B77A CC2B 87B1  4E51 012B 4BD2 8DC9 D62C