Renaming Catalan's constant so Catalan numbers can be defined more na…

[matthewware]

…turally.

This is just an idea to float so the catalan function in Combinatorics.jl won't be in conflict with the constant Base.catalan. I just renamed catalan -> catalan_const. Any comments are welcome!

[waldyrious]

Your editor seems to have automatically converted spaces to tabs, which messes up vertical alignment in editors set up with different tab sizes (and here on github)

[matthewware]

Ah yeah I guess I have vim set up to do that. I can take care of this. I should have read through Style.jl before submitting.

[stevengj]

I don't really understand why this constant is in base at all.

[matthewware]

My guess is that since it's defined in the mpfr libraries it was added into base just incase.

[KristofferC]

Maybe this is not the place to discuss this but these one letter constants keep biting me in the ass. Do they really have to be exported by default? Unicode in code is becoming more and more common so is it really worth to pollute the namespace for some numbers?

[stevengj]

@KristofferC, yes, we've discussed removing everything except for π.

[matthewware]

I don't have strong feelings either way. @StefanKarpinski was okay with renaming. Maybe someone with more knowledge could weigh in on how important and useful it is to have this defined in Base. Maybe @jiahao has an opinion?

[jiahao]

Let's keep this PR focused on catalan -> catalan_const.

e (The natural base) is discussed in #10612.

[stevengj]

If we are going to rename, I would prefer catalan_constant, since const has a special meaning in Julia.

[nalimilan]

I fail to see how we could rename catalan to catalan_constant without also renaming all other constants. Better move them to a Base.Constants module if they are really annoying.

[StefanKarpinski]

I suspect we could just delete the Catalan constant.

[matthewware]

So for now I'll just take the constant out (?) and leave the discussion of the other constants for later.

[waldyrious]

Since all constants' symbols are now single-letter, vertical alignment isn't needed anymore, one space would suffice (this is also valid for the two spaces between the decimal expansion and the expressions: IMO they can now be collapsed to a single space.

[ararslan]

This PR is no longer relevant, as catalan is no longer exported from Base and instead now lives in MathConstants. See #23427.