Square Brackets with Tick

Hi all

I am looking for clarification on an aspect of Unicode bracket pairing,
specifically in relation to the following four characters:

298D; 2990; o # LEFT SQUARE BRACKET WITH TICK IN TOP CORNER
298E; 298F; c # RIGHT SQUARE BRACKET WITH TICK IN BOTTOM CORNER
298F; 298E; o # LEFT SQUARE BRACKET WITH TICK IN BOTTOM CORNER
2990; 298D; c # RIGHT SQUARE BRACKET WITH TICK IN TOP CORNER

These stand out from all other brackets listed in *BidiBrackets.txt* due to
an inconsistency in pairing. I have looked for references online on where
these brackets are used in the wild as mathematical symbols but have been
unable to find anything useful.

All other bracket pairs are listed as opener followed by closer, sometimes
with several code points in between. According to the code point pairs in
the first and second columns of this file, these particular brackets should
be paired as the *first and fourth* and the *third and second*. Intuitively
however, these would actually be *first and second* and *third and fourth*
if one is to expect consistency.

My guess is that there are three possibilities here:
1. The current pairing information is correct and the sequence is irregular
for some historical reason
2. The pairing information is wrong and the sequence is consistent with
other brackets
3. Pairing can be mixed with either left bracket used as a valid opener and
either right bracket used as a valid closer; in this case, the pairing
information is incomplete

I'd be very grateful if anyone could clarify the situation here or if
anyone knows of a resource that describes where such brackets are used in
practice.

Many thanks
Nigel Small
Received on Sat Aug 22 2015 - 11:13:00 CDT