RE: update to xml entities draft

Yes the empty slots in the math alphanumerics are annoying and require extra code to navigate around, but as you know the corresponding characters already existed in the Unicode Standard when we encoded the math alphanumerics (see LetterLike Symbols) and it's Unicode's policy not to encode the same character twice (if possible). So at least it's relatively easy to calculate where the math alphanumerics are. Without the slots it'd be harder.

Murray

Sent from my Windows Phone
________________________________
From: William F Hammond<mailto:hammond@csc.albany.edu>
Sent: ý6/ý23/ý2015 15:12
To: David Carlisle<mailto:davidc@nag.co.uk>
Cc: www-math@w3.org<mailto:www-math@w3.org>
Subject: Re: update to xml entities draft

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

> On 22/06/2015 20:30, William F Hammond wrote:
>> Was nothing done in unicode about the vacant slots in the
>> various math character series, e.g., bbf, cal, frak, nor
>
> If you mean the class="reserved" cells in for example
> http://www.w3.org/2003/entities/2007doc/1D5.html
> then I think Unicode sees those as a feature not a problem that
> needs to be solved.

Yes, that.

>> about cal vs. script ?
> No, I don't know what the prospects of getting anything
> done there are.  At least it seems that a convention for
> OpenType math fonts to have both styles, using the same
> Unicode slots but distinguished by OpenType stylistic
> features is developing.

Yes.

AIUI originally Knuth introduced calligraphic characters to
provide in TeX what mathematicians would write as script
characters.  As things are today, it's possible to use both
in LaTeX.  Given the growing number of levels of hierarchy
in mathematics, there is the tendency for mathematicians to
want ever more families of characters, and, so, for
example, a mathematical author might choose to use \mathcal
for sheaves while using \mathscr for complexes of sheaves.

In this way what was once a distinction between glyphs
becomes a distinction between characters.

Likewise the vacant ("reserved") slots arose, but with less
excuse, from a failure of the larger to community to
appreciate the difference between glyphs and characters, but
it is more egregious since the corresponding characters in
the U+21xx block were carefully chosen in a bygone age
for dedicated usage with particular meaning.

I suppose the "feature" is that the vacant slots exist at
all.

                                    -- Bill