s-->[a,b].
s-->[a],s,[b].

sentence-->noun_phrase,verb_phrase.
verb_phrase-->verb,noun_phrase.
noun_phrase-->determiner,noun.

determiner-->[a].
determiner-->[the].

noun-->[cat].
noun-->[mouse].

verb-->[scares].
verb-->[hates].

faildrivenloop:-
	sentence(X,[]),
	write(X),nl,
	fail.
faildrivenloop.