infer units of quantities

[JacquesCarette]

This was started by @AKM11 (see #377 for some details, and code in Language.Drasil.Misc), but not quite finished. Definitely a good feature to have. As #377 what about a different problem, I'm going to close that one, and the current issue is for remembering to finish the feature itself.

[elwazana]

@JacquesCarette Hello Dr. Carette is there any way for me to help with this issue?

I've looked through #377 and the Language.Drasil.Misc file's relevant code; if I can work on finishing this issue, I would like some clarification on what exactly needs finishing in the feature as you mentioned above as that is still unclear to me.

[JacquesCarette]

Eventually, yes. However, @halonazhao is working on things relating to units right now, and so it would be quite dangerous to do this in parallel. The likelyhood of a difficult merge are way too high.

[balacij]

So, I'm not immediately sure why we want to infer units of quantities. Is it to check that a symbol declaration's unit matches the unit of an expression we're trying to equate it to?

[JacquesCarette]

Yes, it is all about checking coherence. Some expressions might well have units that don't make sense (the same way things can be ill-typed).