From: Jörg Knappen <jknappen_at_web.de>

Date: Mon, 24 Aug 2015 11:39:49 +0200

**Gesendet:** Samstag, 22. August 2015 um 18:35 Uhr

**Von:** "Julian Bradfield" <jcb+unicode@inf.ed.ac.uk>

**An:** unicode@unicode.org

**Betreff:** Re: Square Brackets with Tick
Received on Mon Aug 24 2015 - 04:41:35 CDT

Date: Mon, 24 Aug 2015 11:39:49 +0200

I must admit, although I have seen really lots of mathematical notations, I have never encountered

those particular brackets. I have no intuition how they should pair.

--Jörg Knappen

On 2015-08-22, Nigel Small <nigel@nigelsmall.com> wrote:

> 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

> 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.

That's a strange intuition! Mathematical brackets are expected to pair

with left-right symmetry, not rotational symmetry. As in, for example,

floor and ceiling brackets. The pairing in the file is the natural one.

> 1. The current pairing information is correct and the sequence is irregular

> for some historical reason

That will be the explanation. There is no inherent meaning to the

order of codepoints, it's just convenience.

One of the experts here can probably tell us why these four brackets

happen to be coded in this order.

--

The University of Edinburgh is a charitable body, registered in

Scotland, with registration number SC005336.

> 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

> 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.

That's a strange intuition! Mathematical brackets are expected to pair

with left-right symmetry, not rotational symmetry. As in, for example,

floor and ceiling brackets. The pairing in the file is the natural one.

> 1. The current pairing information is correct and the sequence is irregular

> for some historical reason

That will be the explanation. There is no inherent meaning to the

order of codepoints, it's just convenience.

One of the experts here can probably tell us why these four brackets

happen to be coded in this order.

--

The University of Edinburgh is a charitable body, registered in

Scotland, with registration number SC005336.

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