Added ability to define operation aliases in block form

[mehalter]

Added a second notation for @op macro inside of the @theory

@op begin
  Hom :→
  compose :⋅
end

Also updated tests to make sure both notations work, and found a typo/bug in one of the ParseError definitions

[jpfairbanks]

Cool! What about doing the syntax like

@op begin
  (→) := Hom
  (⋅) := compose
end

That makes more sense from a math notation perspective.

[mehalter]

I just made a change that will currently allow you to define them in the notation that James brought up, or the same notation that is used for the single line definitions. Once we decide on a specific version to use, I can remove the other in the if statement. We can agree to use both, but I think I would prefer to settle on a single notation.

[epatters]

I would also strongly prefer to settle on a single notation. I think I slightly prefer James' notation, but here I don't feel as strongly.

[jpfairbanks]

Yeah I think the Hom :+ is ooogly. let's just do the := notation. and then we just forbid using := as a unicode name for a Gat term.

[mehalter]

Cool I think this PR is ready once the tests pass.

[epatters]

For consistency, shouldn't we use the same syntax in the short form of @op, e.g., @op (→) := Hom instead of @op Hom :→?

[jpfairbanks]

Yeah I think that is more consistent

[jpfairbanks]

New code looks good to me. I like this interface a lot