I am reading a computer science paper and have come across some notation that I am unfamiliar with.

it says to consider functions from $\mathbb{R}^N$ to $]-\infty,\infty]$

is this the same as writing $(-\infty,\infty]$?

to use another example, is this true:

$x \in ]4,6] \iff 4 < x \leq 6$

  • 2
    $\begingroup$ Yes, using inverted brackets is an alternative to parentheses for use in intervals. $\endgroup$ – Hayden May 12 '15 at 7:50
  • $\begingroup$ thanks, do you know if one is considered more "correct" than the other? or is it just a matter of personal preference? $\endgroup$ – guskenny83 May 12 '15 at 8:30
  • $\begingroup$ From my experience the use of parentheses is by far the more common notation. Personally, I do prefer the inverted brackets as it eliminates the issue of possibly confusing something like $(a,b)$ with the point $(a,b)\in \mathbb{R}^2$, so some authors continue to use the inverted brackets in lieu of the parentheses because of this advantage. So it depends on how you define "correct", but ultimately both are fine. As is the case with all notation, as long as it is consistent and defined, there is no "correct" notation (though there is conventional notation for some things). $\endgroup$ – Hayden May 12 '15 at 8:49

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