Picat – A new logic-based programming language

Looks like an interesting project.

The license or terms-of-use seem weird: "Picat can be used for any fair purpose, including commercial applications. The C source code is available to registered developers and users free of charge. The project is open to anybody and you are welcome to join, as a developer, a sponsor, a user, or a reviewer. Please contact picat@picat-lang.org"

Why make things complicated with these conditions? If you are going to allow source access, why not use a standard open source license. If you aren't, if you want to control of the language for some purpose, make it clear this is a commercial product.

The GPL (and other standard open source licenses) are a real commercial licenses at this point. Roll-your-own software licenses seem a lot like roll-your-own device device drivers - might have made sense in yesterday's world but not today.

Here's an article explaining it's features with more mainstream terms.

http://www.hakank.org/constraint_programming_blog/2013/09/a_...

Another language which involves both constraint programming and imperative programming is Alma-0[1]. While Alma-0 doesn't seem that much more than a toy language, I always liked the backtracking + standard-loops feature. It seemed offer clarity plus incredible power.

I would wonder if Picat has similar feature (to implicit backtracking in imperative loops)?

[1] http://en.wikipedia.org/wiki/Alma-0

I used to love Prolog, but Prolog is not general purpose. This has 'pi', 'cat', some imperative, and prolog taste in it...most interesting.