Mercury is a Prolog-derived language with static types and clause determinism annotations for static compilation. In Prolog slang, Prolog SLD resolution wouldn'

Mercury is a Prolog-derived language with static types and clause determinism annotations for static compilation. In Prolog slang, Prolog SLD resolution wouldn't be called "constraint solving" though it certainly can solve constraints over finite domains via exhaustive search. Constraint solving as a term is typically associated with finite and interval constraint propagation methods on top of Prolog. Actually, Prince (fka Prince XML) is a commercial CSS renderer for paged media that has been implemented using Mercury, and I'd say is even a major showcase for Mercury. But unfortunately, Prince isn't open source, and what little is known of its internals is that it doesn't use much Prolog-style indeterminism/backtracking but is quite procedural in nature. Maybe CSS matching is implemented using Prolog-style unification/pattern matching but CSS selector matching uses eg. priorities whereas Prolog matches applicable clauses in document order, so I don't know about that. Actually, I'd love to hear about that from Prince developers hanging around here ;)