From: Timothy Menzies (tim@menzies.com)
Date: Fri 14 Apr 2000 - 14:57:54 MEST
why use the cut? bassert(X) :- assert(X); retract(X), fail. bretract(X) :- X,(retract(X);assert(X), fail). ----- Original Message ----- From: "Jan Wedekind" <unoh@rz.uni-karlsruhe.de> To: <prolog@swi.psy.uva.nl> Sent: Friday, April 14, 2000 6:24 AM Subject: indeterministic ASSERT and RETRACT > I would like to write an application in prolog, that will extract > knowledge from english sentences. I think, this program should add > the learned predicates to the prolog-database by using "assert/1". > But the problem is, that "assert/1" has no indeterministic (I think you > all know this). So I do not now, how to write an indeterministic rule, which > will clean up all created predicates on backtracking. Can anyone propose > a solution for this? > The reason, why I am posting to the SWI-Prolog specific mailing-list is, > that perhaps there is a possibility to solve this problem by creating a > new predicate "xassert" with the C-interface. However I do not now, how to > create such a predicate: The problem is, that after a cut-and-fail > (..., assertx( ... ), !, fail ) SWI-Prolog does not inform the C-routine > "PL_assertx" about the failure. > If anyone has an answer to this problem, tell me! If there is a simple > PROLOG-solution for this problem, forgive me! > > Jan Wedekind, student at University of Karlsruhe, Germany. > > > ---------------- > * To UNSUBSCRIBE, please use the HTML form at > > http://hcs.science.uva.nl/projects/SWI-Prolog/index.html#mailinglist > > or send mail to prolog-request@swi.psy.uva.nl using the Subject: "unsubscribe" > (without the quotes) and *no* message body. > > ** An ARCHIVE of this list is maintained at > > http://hcs.science.uva.nl/projects/SWI-Prolog/mailinglist/archive/ >