Wrapping `#(⋅)`

[jasonhemann]

In e.g. queens.pl, there are several variables that need the # on them in order for the program to support monotonic CLP(ℤ). Would you accept a PR adding that? Happy to put it up.

[triska]

First: Excellent point! Almost all existing CLP(ℤ) programs are wrong because they are incomplete: Solutions exist and are found in certain usage modes but not in others. Using the monotonic execution mode makes many of these programs correct, and requires the # wrapper for integer variables.

So, I agree that we should make this change.

At the same time, I want this to be a resource that can be used with several different Prolog systems, notably also GNU Prolog as far as possible. Currently, the most conforming Prolog systems are SICStus, Scryer, and GNU, and I would like to make examples work as far as possible in all these systems.

So, the question is when to best introduce the # wrapper in code examples. In my opinion, a sensible time would be when GNU Prolog supports it.

For now, the clpz repository would certainly benefit most from such adaptions, both in the documentation and also in the code examples: https://github.com/triska/clpz I would greatly appreciate if you could take a look, and think about how to best introduce the monotonic mode in the documentation, which currently does not mention it at all.