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angle brackets in math (Was Re: several messages ...)

From: William F Hammond <hammond@csc.albany.edu>
Date: Fri, 23 May 2008 14:26:21 -0400
To: public-html@w3.org, www-math@w3.org
Message-ID: <i78wy0ri5u.fsf_-_@hilbert.math.albany.edu>

David Carlisle <davidc@nag.co.uk> writes:

> The mapping currently defined for lang to 27E9 (MATHEMATICAL LEFT ANGLE
> BRACKET) is definitely the correct one and if the definition of rang is
> changed at all from its html4 definition it should be to this and not to
> U+3008 (LEFT ANGLE BRACKET)
>
> The original definition  was to U+2329 (LEFT-POINTING ANGLE BRACKET)
> which is in the 2xxxx block of technical symbols not CJK punctuation,
> and the name "rang" comes from ISOTECH entity set for technical
> publishing. So this entity has always been intended for mathematical use.

(In my Firefox (2.0.0.14) it seems that only 2329 and 232A are appropriately
stretchy.)

It strikes me, however, that to the extent presentation markup can be
maximally semantic (which is related to what one might be able to coax
out of most mathematical authors some day), these brackets and other
stretchy balancers should, for presentation markup, be deployed via
<mfenced> (the list constructor).

Routes for this include LaTeX's \left<...\right> or gellmu's \vect[<>]{...}
and \bal[<>]{...} [in releases so far, actually, \balab{...}].

Then might one hope that user agents will durably pick up the right things
when rendering <mfenced open="&lt;" close="&gt;">...</mfenced>?

Beyond that one might hope with <mfenced> that user agents will durably
pick up the right things with any of the aforementioned balancing pairs
as values for the <mfenced> attributes.

Or is this asking too much of user agents?

                                    -- Bill
Received on Friday, 23 May 2008 18:26:58 GMT

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