The ECLiPSe Constraint Logic Programming System is designed for solving combinatorial optimization problems, for the development of new constraint solver technology and their hybrids, and for the teaching of modelling, solving and search techniques.
See brownbuffalo.sourceforge.net for code examples: constraint logic used to solve word puzzles.
Very usefull for our project and easy to use also for people not trained on logic programming. Learned a lot about logic constraint programming. Very good documentation.