🚀 go-pugleaf

In article <1992Aug25.074623.25450@greco-prog.fr>, billaud@greco-prog.fr
(Michel BILLAUD) writes:
|> In article <meskes.713709771@ulysses>
|> meskes@ulysses.informatik.rwth-aachen.de (Michael Meskes) writes:
|> 
|> > Can you program a IF...THEN...ELSE in Prolog without using the cut?
|> 
|> No. a proof by contradiction:

[ proof deleted ]

I am sorry to contradict your contradiction ;-)  As someone else has
pointed out, it _is_ possible to program if-then-else without cut
IN CERTAIN SPECIAL CASES.

Canonical example:
  IF X >= Y THEN Max := X ELSE Max := Y END

Prolog translation:
  % max(+X,+Y,?Max): Max is the maximum of X and Y
  max(X,Y,X) :- X >= Y.
  max(X,Y,Y) :- X < Y.

This works because < happens to be the logical negation of >=
provided that both arguments are ground.

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