CW 446

Peter Van Weert, Jon Sneyers, Tom Schrijvers, Bart Demoen
To CHR^¬ or not to CHR^¬: Extending CHR with negation as absence

Abstract

In this exploratory paper, we introduce CHR^¬, an extension of the CHR language with negation as absence, and we illustrate how the added expressiveness allows CHR programmers to write more declarative and concise rules. We show the difficulties of integrating negation with the conventional execution mechanism of CHR. A formal operational semantics for CHR^¬ is presented, and its theoretical and practical implications are evaluated critically. We introduce a source-to-source transformation from CHR^¬ to regular CHR.