7 CHR: Constraint Handling Rules

This chapter is written by Tom Schrijvers, K.U. Leuven, and adjustments by Jan Wielemaker.

The CHR system of SWI-Prolog is the K.U.Leuven CHR system. The runtime environment is written by Christian Holzbaur and Tom Schrijvers while the compiler is written by Tom Schrijvers. Both are integrated with SWI-Prolog and licensed under compatible conditions with permission from the authors.

The main reference for SWI-Prolog's CHR system is:

• T. Schrijvers, and B. Demoen, The K.U.Leuven CHR System: Implementation and Application, First Workshop on Constraint Handling Rules: Selected Contributions (Frühwirth, T. and Meister, M., eds.), pp. 1--5, 2004.

• 7.1 Introduction
• 7.2 Syntax and Semantics
  • 7.2.1 Syntax
  • 7.2.2 Semantics
• 7.3 CHR in SWI-Prolog Programs
  • 7.3.1 Embedding in Prolog Programs
  • 7.3.2 Constraint declaration
  • 7.3.3 Compilation
• 7.4 Debugging
  • 7.4.1 Ports
  • 7.4.2 Tracing
  • 7.4.3 CHR Debugging Predicates
• 7.5 Examples
• 7.6 Backwards Compatibility
• 7.7 Guidelines