FaCiLe is a constraint programming library on integer and integer set
finite domains written in OCaml. It offers all usual facilities to create
and manipulate finite domain variables, arithmetic expressions and
constraints, built-in global constraints and search and optimization goals.

FaCiLe allows as well to build easily user-defined constraints and goals,
making pervasive use of OCaml higher-order functionals to provide a simple
and flexible interface for the user.

WWW: http://www.recherche.enac.fr/log/facile/