Add option to keep epsilon in get_word()

[jurajsic]

Needed for Noodler. It should probably be some enum argument, maybe we should have some general argument that says whether epsilon should be handled as normal symbol for all functions that work with epsilons.

[koniksedy]

LGTM. I agree that some enum with potentially more options would look nice.

[Adda0]

Could you add this general enum in this PR? Not sure about the names? Simply to have all the future bool flags discoverable easily by looking for enum classes, but also so that we can start using this flag. I think there were already a few functions where we were talking about handling epsilons as normal symbols.

If you need this urgently, just please add a TODO to replace this bool flag with an more general epsilon handling enum class.

[jurajsic]

I am also thinking whether instead of bool/enum, we change fist_epsilon to std::option<first_epsilon> and if it has a value, there are epsilons, otherwise not.

[Adda0]

Yeah, that should be done 👍 It is probably a better approach in this particular case. In the future, with a full bool flags as bit fields redesign, we will see what the best approach will be, but for now, this sounds like a pretty good idea.