The SVN repository seems to be here.
“written by Pieter Wuille”
Yep, that’s probably it! Good find.
“Constraint Handling Rules (CHR)  is a high-level, declarative language, originally
designed for the implementation of user-defined, application-tailored, constraint
solvers in a given host language. Nowadays CHR is increasingly being
used as a general programming language for a wide range of applications —
multi-agent systems, type systems and natural language processing, to name a
few — and for the study of algorithms.”
“This paper presents CCHR, a CHR system embedded in the C programming
language, that compiles to low-level C code… CCHR program performance comes close to matching that
of native C, and easily outperforms other CHR implementations.”