clpz

Check out the CLP(ℤ) library by Markus Triska, who is also the author of Scryer Prolog. It defines new comparison predicates that lets you use bidirectional logical programming on standard integers with standard math operations. https://github.com/triska/clpz

As pointed out in the comments in the article, these kinds of logic puzzles are easier to solve using constraint programming than "regular" logic programming. For example, see the solution to the Zebra Puzzle here: https://www.metalevel.at/prolog/puzzles which uses CLPZ[^1]. [^1]: https://github.com/triska/clpz

Prolog and CLP is an interesting and powerful combination as documented here: https://www.metalevel.at/prolog/optimization. In particular the CLPZ library is very powerful: https://github.com/triska/clpz.

Does anyone know if there's a datalog-like embeddable language that is suitable for simple integer constraints (the sum of a, b, c, and d must be e; e=10.,b>2.)? For prolog, there's apparently https://github.com/triska/clpz/ But I really just want some simple constraints-oriented form validation (you have 100 points, please feel free to by x's for 1 point each, y's for a cost of 5 points. You don't have to spend all points - with feedback of how many points are left as more x and y are bought. But for more variables, where there are clear rules that can be modeled naturally as constraints rather than with state and callbacks on change). Ed: specifically for forms, there's https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/HTML... - but it feels like it gets messy with interdependent fields.