Subject: not with trace or not with fail ???

From: "jean-F. Dazy" <[email-masked]>
Date: Mon, 27 Nov 2000 11:23:43 +0100

?- not(v).
ERROR: Undefined procedure: v/0

?- unknown(_ , fail).
Yes
?- not(v).

Yes

it is dangerous  !
2 differents semantics ????

jfd