% original version at http://www.csupomona.edu/~jrfisher/www/geolog/inf.gl

:- op(1200,xfx,':=').
:- op(1199,xfx,'=>').

:- dynamic(p/1).
:- dynamic(q/1).
:- dynamic(answer/1).

flag(keywords).
flag(quiet).
flag(quick).

[a1]	:= true => p(a).
[a3]	:= p(f(a)) => answer(p(f(a))).
[]	:= answer(_) => goal.
[a2]	:= p(X) => p(f(X)) ; q(X).
[a4]	:= q(X) => answer(q(X)).