[q-lang-users] Newbie: Backtracking again

[Mele, G. (MH) <Gre...@ma...>]

Thanks in advance.
 
I dont understand the queens algorithm enough to see how backtracking works
by the fail instruction.
 
I would like to have a prolog-like system:
ie the classic genealogical database
 
 
father(a,b).
father(b,c).
father(c,d).
 
ancestor(X,Y) :- father (X,Z), ancestor (Z,Y). 
 
Is this possible?
Or is there another simple example of backtracking using the fail
instruction that I could ponder over?
 
 
Greg
 
 
 
THIS E-MAIL IS CONFIDENTIAL.  If you have received this e-mail in error,
please notify us by return e-mail and delete the document.  If you are not
the intended recipient you are hereby notified that any disclosure, copying,
distribution or taking any action in reliance on the contents of this
information is strictly prohibited and may be unlawful.  Eastern Health is
not liable for the proper and complete transmission of the information
contained in this communication or for any delay in its receipt.