Is there a notation for referring to an interval when one does not know a priori whether it is open or closed (or some combination thereof)?
e.g. 1) if one were trying to determine the interval of convergence of a power-series representation of a function and had determined that the centre is $x = c$ and the radius is $r = R$, but do not yet know whether the end points $x = c \pm R$ are included or not, is there any way to refer to such an interval (other than the way I have done here)?
e.g. 2) any situation in which the inclusion / exclusion of the endpoints is immaterial to the point at hand.
I tried searching for this here and on other sites, but the language is tricky, as anything about intervals or end-points “not being known” automatically brings up results related to the end-points not being determined (or their order not being known) etc.
I thought perhaps there’d be something like $[/(\, a, b\, )/]$ or $[/(\, a, b\,]/)$. Would be very interested if anyone knows of a common convention.