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Grown-up maths people who don't need to do exams any more: when's the last time you used interval notation?

I'm talking about things like (1,3] for "the interval between 1 and 3, including 3 but not 1".

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@christianp occasionally, but it feels ambiguous enough in non-math papers to warrant a more explicit notation

@christianp I was explaining the group structure on elliptic curves, using rational points mod p. So I talked about the points being of the form (x,y) in [0,p)^2.

Or similar.

@christianp
Yesterday; a parameter for an ML algorithm has allowable values in \((0,1]\).

@christianp when I have to discuss intervals with other people I'm writing code with. Sometimes I still get thrown off by my French colleague using Bourbaki's \(]1,3]\).

@christianp That said, we often do switch between saying \(x\in(1,3]\) and \(1<x\le 3\).

@christianp Not lately, now that I think on it... But I don't regularly deal with continuous anything. And I'm not a topologist. There is very little cause for intervals in algebraic number theory.

@christianp There isn't much call in what I've worked on for leaving off the endpoints of an interval. I looked up the instances I could remember offhand where we did have to do that (e.g., taking a parameter in the unit interval all the way to 0 or to 1 led to a degenerate case of some kind). We ended up not using the mixed-bracket notation in the final papers, though it's possible we used it on a whiteboard.

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