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Showing posts from September, 2009

PPDP 2009 over and Prological SYB code goes live

Just tried to send an email to what I thought would be the cafe mailing list of the Association of Logic Programming (ALP). My message bounced. Sigh! Anyway, here is the message and below you also see the content of the README file for the tiny code distribution for scrap[p]ing boilerplate prologically. From: Ralf Laemmel rlaemmel@gmail.com To: Alp-cafe-request@babel.ls.fi.upm.es Date: Thu, 10 Sep 2009 22:57:11 +0100 Subject: post-PPDP 2009 greeting Not sure whether this mailing list is actually working (because I haven't seen any traffic since June when it all started) but I thought it couldn't hurt to send a short post-PPDP 2009 greeting. António Porto, Francisco J. López-Fraguas, Pedro Quaresma, Ana Paula Tomás, and their collaborators have put together a great conference event. The program was really packed; perhaps even a bit stressful :-) I would have loved to interact a bit more during additional breaks and panels. For what it's worth, I have uploaded the SYB source

Decreasing salaries with addition

There are some parts of my PPDP 2009 invited talk that didn't make it into the short paper for that talk. In particular, I played a bit with the feature interaction of traversal (SYB) and using predicates in different modes. The use of multi-mode predicates is one of the exciting aspects of logic programming. (It is somewhat disputed how crucial or useful it is, but it is impressive/expressive anyhow.) For instance, beginners are always surprised to see that one can use append/3 to both .... well ... append but also take apart lists. So I considered the question how to use such multi-modeness, if at all, perhaps even usefully, in the context of traversal programming. Here, we would expect traversal predicates to serve the normal forward direction (traverse first argument, compute second argument) and the unusual backward direction . Let's consider the following, recession-inspired scenario for the sake of the argument: We certainly know how to increase salaries (say by 1 $)