SWI Prolog also comes with constraint solvers. It has CLP(B) (booleans), CLP(FD)(finite domain), CLP(Q,R) (rationals and reals) and CHR (constraint handling rul

SWI Prolog also comes with constraint solvers. It has CLP(B) (booleans), CLP(FD)(finite domain), CLP(Q,R) (rationals and reals) and CHR (constraint handling rules). These come as standard libraries, no additional installation needed. If you want to get started, I recommend starting with CLP(FD) as that has a lot of tutorials and is highly compatible between Prolog implementations.