Mathematicians: variables are named using Latin, Greek, Fraktur, Hebrew and Linear B letters in bold, italic, script, sans-serif and serif forms.

Also mathematicians: I need some brackets. Guess I'll use good ol' parentheses again! 😎

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@tpfto wow! No, I hadn't seen that. Pretty bold to use 十 as a *name*!

@christianp The apparent diversity in letter styles still has its root in the same problem: "I need a letter. Guess I'll use good ol' 'K' again!"

@jsiehler yeah, I suppose I should have talked about other annotations like dots, accents and sub/superscripts. I wonder if anyone draws stuff on top of their brackets, like with the integral symbol: ∮, ⨎, ∱

@christianp (a b) (with some space) for cyclic permutations.

Fun fact @zorkow's SRE has a heuristic to detect them because Nemeth has a braille notation for cycles.

Also fun fact, sometimes authors will just add space between (AB) because they just don't want it that tight right there. Hilarity ensues.

@pkra yes! I knew there was another one I use regularly, but it wasn't coming to mind

@christianp Another one missing from the list: open intervals.

I find (a, b) very confusing when I work with tuples in the same context.

On top of that, I find intervals with a single open end somewhat aesthetically unpleasing.

(a, b] seems to be the most prevalent notation. The bracket's "directions" match, though the bracket's types don't.

[a, b[ is a notation that seems to be popular in Germany, but which I haven't seen anywhere else much. (It's due to Bourbaki, I have been told)

A notation I invented and use myself in these cases are in fact square brackets with superimposed circles for open ends of intervals.

It is inspired by the way one may use to draw (half-)open line segments.

@esclear yes, good one! That reminds me to find the paper I started writing about parsing notation, where I collected a list of things like this

@christianp Another kind of bracket is the \( [\![\cdot ]\!] \) notation used for a valuation in logic. In non-distributive modal logic we also have \( (\![{\cdot}]\!) \) 😅

I just noticed that inner products are missing from that list 🤔

Sure, here's an example from the lecture notes of a course I'm taking this semester.

Although I personally refuse to use this notation and use angle brackets instead.

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