%Prolog example developed by Dr. Klerer, CSUSB
:-dynamic(once/0).

one(X) :- X=1.
two(X) :- X=2.
two(X) :- X=3.

uniq(G) :- call(G), ((once, retract(once),!, fail); 
		(asserta(once), fail)).
uniq(_) :- once, retract(once).

u(G) :- call(G), (once, retract(once),!, fail; 
		asserta(once), fail) ; once, retract(once).

one :- one(_), ((once, retract(once),!, fail); 
		(asserta(once), fail)).
one :- once, retract(once).

two :- two(_), ((once, retract(once),!, fail); 
		(asserta(once), fail)).
two :- once, retract(once).


r :- repeat, ((once, retract(once),!, fail); 
		(asserta(once), fail)).
r :- once, retract(once).

:- write('uniq(Goal) loaded'), nl.