The chr library implements constraint handling rules (CHRs). It includes a compiler, which translates CHR programs into ECLiPSe programs, and a runtime system. Several constraint handlers are provided in example files in the directory chr.
The current chr library has now been modified to function correctly without the Opium debugger, which is no longer supported. In addition, the Prolog code produced by the chr command is now more readable.
In addition, there is now an experimental extended implementation of CHRs. This extended implementation is faster than the existing chr library, and contains some extensions and changes. This is described in section 8.9.