make \minus equivalent to - operator #26193

[epithet]

Add the typographically more correct minus sign − (\minus) as an alternative for the traditionally used hyphen-minus - (which is readilly available on all keyboard layouts).

To many, it is aesthetically more pleasing because it has the same width as +. But the main advantage is that it would allow for copy-pasting negative numbers (and to some degree, formulas with subtractions) from correctly typeset PDF/HTML/... documents into Julia code. Actual code snippets can also accidentally be "beautified" by CMS/blog software, word processors, e-mail clients, etc.

Fixes #26193.

[JeffBezanson]

Welcome and great first PR! Seems like a good idea.

[JeffBezanson]

This should make it work as an operator, but we also parse - as part of negative numeric literals, so some additional changes are needed to make that work.

[JeffBezanson]

Oh wait I'm wrong, negative literals go through parse-unary so they're already handled. There should be a test for it though.

The remaining case is floating point exponents, e.g. 1.0e-1; we might want to allow the minus there as well.

[JeffBezanson]

−= should maybe also be added.

[epithet]

@JeffBezanson very good points! I'll see what I can do.

[epithet]

@JeffBezanson

• have I missed something? (implementation or test coverage)
• should the documentation mention all these cases?
• there seem to have been some unrelated hiccups in the CI pipeline, see commit bc48a59

[epithet]

btw: I remembered the existence of rlwrap only halfway through. Could be helpful to mention it here, for example: https://github.com/JuliaLang/julia/blob/bb5b98e72a151c41471d8cc14cacb495d647fb7f/doc/src/devdocs/eval.md#parsingid-dev-parsing
(seemed too insignificant for a separate PR/issue, and not entirely off-topic)

[oscardssmith]

triage approves.