A Prolog Constraint Handling Rules Compiler and Runtime System, Special Issue of the

We introduce the most recent and advanced implementation of constraint handling rules (CHR) in a logic programming language. The Prolog imple-mentation consists of a runtime system and a compiler. The runtime system utilizes attributed variables for the realization of the constraint store with eÆcient retrieval and update mechanisms. Rules describing the interactions between constraints are compiled into Prolog clauses by a compiler, the core of which comprises a small number of compact code generating templates in the form of denite clause grammar rules.