[Q] How do I implement a range table?

[rmgaray]

Hello!

Admittedly my logic programming is not very good, but I was wondering if it is possible to create an infix rule like this:

range[a, b, x]

where a and b are integers defining a closed interval in Z and x can be any integer within the interval. The most straightforward implementation is this one:

range[x] := x = 0
range[x] := range[y], x = y + 1, x <= 10
?[x] := range[x]

where a = 0 and b = 10. But as you can see, I need to hardcode a and b and I can't really have the range[a, b, x] rule as I originally stated. Is this an inherent limitation of Datalog? I'm thinking this can probably be implemented as a custom fixed rule that takes parameters a and b, but I wonder if something like this could be done only using CozoScript.

Thanks in advance and congrats on the project, I think it's really cool.

[zh217]

What you are asking for is infinite relations: as a and b are bindings, the relation represented by range must be (at least conceptually) infinite. This has been studied in the academic literature as an extension to Datalog, but I am not aware of any practical Datalog implementation that supports it.

However, writing it in the following way is perfectly acceptable in CozoScript:

range[x] := x = $lower
range[x] := range[y], x = y + 1, x <= $upper
?[x] := range[x]

and at query time you can pass in $lower and $upper as parameters. Does this work for you?

[rmgaray]

I think it will work for my use case, yes.

Thanks for the explanation, I will look up infinite relations since now I am curious about them.