Newbie to GProlog - Is it ISO?

[Paulo J. Matos aka PDestroy]

Hi all,

I'm studying Prolog and my teacher recommends Sicstus
Prolog. Although she recommends it I prefered Gprolog since it is
free. But now I'm finding gprolog a bit strange. My Prolog book
is Programming in Prolog (4th ed.) from Clocksin.
There are two questions about predicated that show up in sicstus
and in clocksin and afaik are not in gprolog. One is not. The
negation predicate fails when its arguments succeeds and
vice-versa.
The other is randseq. It builds a sequence with numbers randomly
ordered.

I've tried to write this function in gprolog but for that I need
not, since there is no not and I can't write a not in prolog I'm
stuck.

Can anybody help?

Best regards,

-- 
Paulo J. Matos aka PDestroy : pocm(_at_)rnl.ist.utl.pt
Instituto Superior Tecnico - Lisbon    
Software & Computer Engineering - A.I.
 - > http://www.rnl.ist.utl.pt/~pocm 
 ---    
        Yes, God had a deadline...
                So, He wrote it all in Lisp!