[Solved partially] How to have non pairing bracket?

[Horus]

I've searched the Help, the forum and the Math guide but can't seem to find any answer.

So, is it possible to have non pairing bracket?

In case you ask, there are at least two situations where it's necessary:
1. Intervals:
For example: (a, b] or [a, b)
Or in ISO notation: [a, b[ , ]a, b] or ]a, b[

2. Presentational:
f(x) = x^2 if x < 0
= - x^2 if x >= 0
Here, by convention, we would put a big "{" after the equal sign and group the right members into one block.

[keme]

Use the left and right keywords. They allow unmatched pairs, and make brackets scale to content.
1: e.g. left [ a,b right [
2: f(x)=left lbrace stack{x^2 if x<0 # -x^2 if x>=0} right none

[Horus]

Thanks for the answer.
I've just found the answer in OOOforum at http://www.oooforum.org/forum/viewtopic.phtml?t=77489 (off-topic: I'm wondering why that forum is also called OpenOffice.org forum!??)

Yes, the word "none" solves problem #2. This deserves a section in Math Guide or in FAQ.

For problem #1, I had actually thought of using string: "("a , b"]" but it doesn't look good.
Using left and right keywords doesn't look good either. Try this and compare the visual effects:
(a,b) newline
[a,b] newline
"("a , b"]" newline
left ( a,b right ] newline
Scalable brackets are too "thin", esp on "[]"

I really think it would be good to have some "solitary" brackets.