TITLE: Notation for an interval when you don't know which bound is greater
QUESTION [51 upvotes]: Is there a notation in English written mathematics for $$\textit{the interval of all points lying between two real numbers $a$ and $b$}$$ when you don't know which of $a$ and $b$ is greater?
Which one is greater is completely irrelevant for what I am writing, and I would like to avoid making the text heavier as much as possible.

Suggestions that have been made so far that rely on external notions:
$$[\min\{a,b\}, \max\{a,b\}]\qquad \operatorname{Conv}(a,b)$$
Suggestions for a brand new notation: $$(a,b]^*\qquad (\{a,b\}]\qquad (a\nearrow b]\qquad /a,b/\qquad \left(\begin{matrix}a\\b\end{matrix}\right]^\star$$
$^\star$ intervals open at the lower bound and closed at the higher bound, whichever of $a$ and $b$ they are.
Some other options:  

Assume wlog that $a<b$
Make explicit that the notation $[a,b]$ doesn't imply $a<b$.

REPLY [2 votes]: While I appreciate your goal to avoid sophistication than necessary, you might be a typical victim of obscurity. Because while you are trying to prevent a needless assumption on the ordering you are introducing a mental load on the reader with "an interval defined by two endpoints with no known preference". 
However this is already the default stance of the reader. Nobody sets out to read $[a,b]$ as I wonder whether $a>b$?. In fact this is the reason why we use consecutive letters. Consider $[\beta, \Phi]$ it doesn't have the same effect does it? It has more certainty attached to it as if they were defined somewhere else and we are reading from the middle of a paragraph.
Hence if you want to keep things simple just use $\{a,...,b\}$ it is a set notation thus no ordering is needed per se and also it is a common enough construct which implies continuation from one to the other in some sense regardless of the order.