Handling special symbols in Mata: epsilons, dont care(s), markers in strings, etc.

[Adda0]

We need to decide what to do with a potential set of epsilon symbols with a default epsilon always being present, then dont care symbol, and how do we want to define marker epsilon symbols for strings in Mata.

Debugging constants leaking out:

Me neither. I think this is some debug value from when we were implementing this leaking out. It should be a special marker (epsilon) symbol as used in transducers, for example in noodlification, but never standardized as a special epsilon symbol. Hence, it was only for debugging back then.

Originally posted by @Adda0 in #501 (comment)

[jurajsic]

Isn't marker the symbol used in transforming replace_all to NFT?

[Adda0]

There are two current symbols which use the name marker. One is those in noodlification, the other is as you say. Yours is an implementation detail that needs to be hidden, the other is a strings-specific symbol which should be defined only for strings operations. But on the other hand, we might want to be able to pretty-print these second symbols, too. Needs some thoughts.

[jurajsic]

The ones in noodlifications are specific for noodlifications and are different from the one that is printed. We do not need to print it, it is just part of noodlification.

What do you mean strings operations, which ones? Only those for noodler? I do not think we should print them either.

[Adda0]

Yeah, noodlification. If we do not want to print them (as was used in the linked issue above for debug purposes), that makes this much easier. Still, we need to revise how epsilons and dont care(s) are defined and how and if should one be able to define new special symbols for their specific use cases.