Zulip Chat Archive

Stream: general

Topic: Symmetric difference notation


Yaël Dillies (Mar 26 2022 at 14:57):

The current notation for docs#symm_diff is Δ. This conflicts with the use of Δ as a variable in docs#simplex_category.eq_comp_δ_of_not_surjective'.

What should we do? Change the notation to another unicode triangle? Localize it?

Yaël Dillies (Mar 26 2022 at 14:57):

This conflict is preventing me from slightly tweaking the imports in #6476.

Reid Barton (Mar 26 2022 at 15:14):

Certainly letters shouldn't be notation

Reid Barton (Mar 26 2022 at 15:16):

At least not notation for operators, that's just weird

Reid Barton (Mar 26 2022 at 15:16):

(ω\omega as localized notation for omega seems ok for instance)

Reid Barton (Mar 26 2022 at 15:17):

https://unicode-explorer.com/c/2206 suggests that it but perhaps also other unicode characters could be used for symmetric difference

Reid Barton (Mar 26 2022 at 15:18):

(and that it might also be used for more interesting things)

Bryan Gin-ge Chen (Mar 26 2022 at 16:53):

As the one who introduced the notation, I'm perfectly fine with it being changed or localized.

(Actually, I think I copied it from this snippet but I'm happy to take the blame!)

Kyle Miller (Mar 26 2022 at 17:01):

I think it's common to find a stylized capital delta in the literature - i.e., a triangle. Options:

I found one place that suggested to use the first symbol for symmetric difference. Whatever the choice, localizing the notation seems like a good idea.

Yaël Dillies (Mar 26 2022 at 17:04):

looks rather horrendous to me, so what about using ? Also, do we want to localize or rather leave a comment saying "localize as soon as you need the notation for something else"?

Yaël Dillies (Mar 26 2022 at 17:04):

I don't know how far we are from having Laplace.

Kyle Miller (Mar 26 2022 at 17:06):

Maybe prefix vs infix is enough to disambiguate them anyway.

Eric Wieser (Mar 26 2022 at 17:06):

In the short term, you can use \fr<<>> to escape the identifier in the downstream lemma

Yaël Dillies (Mar 26 2022 at 17:06):

\f<<>> is enough btw

Eric Wieser (Mar 26 2022 at 17:06):

I probably meant to say that,

Yaël Dillies (Apr 07 2022 at 11:58):

#13217


Last updated: Aug 03 2023 at 10:10 UTC