🚀 go-pugleaf

In article <5100@sersun1.essex.ac.uk> palmm@essex.ac.uk (Palmer M J)
writes:

#  Some systems (e.g.  Qunitus Prolog) allow you to use the form _VarName. 
#  This is still an anonymous variable but with a name.  You might like to
#  try this. 

Forgive my pedantry, but (in Edinburgh Prolog) ocurrences of variables
with the same name are equal to each other, even if the name begins with
_.  So _A and _B, etc., are not anonymous variables.  The point is that
the singleton variable check is not applied to such variable names. 

Therefore such code as

    different(A,A) :-
       !,
       fail.

    different(_A,_B).

does not generate a singleton error message.  (NB This predicate is not
the best way to test whether _A and _B are different, unless you want to
unify them if possible.  It's just a way to illustrate the magical
property of the variable names _A and _B.)

-- 
////  Advice to dieters:          ////  Ken Johnson, A I Applications Institute
////    Never eat more than       ////       80 South Bridge, EDINBURGH EH1 1HN
////    you can carry.            ////                 E-mail ken@aiai.ed.ac.uk
////               -- Miss Piggy  ////     phone 031-650 2756  fax 031-650 6513