From: Murray Sargent <murrays@exchange.microsoft.com>

Date: Tue, 23 Jun 2015 18:58:35 +0000

To: William F Hammond <hammond@csc.albany.edu>, David Carlisle <davidc@nag.co.uk>

CC: "www-math@w3.org" <www-math@w3.org>

Message-ID: <7f66244ee065431c8bcfa41c6c8ea6d1@DFM-TK5MBX15-06.exchange.corp.microsoft.com>

Date: Tue, 23 Jun 2015 18:58:35 +0000

To: William F Hammond <hammond@csc.albany.edu>, David Carlisle <davidc@nag.co.uk>

CC: "www-math@w3.org" <www-math@w3.org>

Message-ID: <7f66244ee065431c8bcfa41c6c8ea6d1@DFM-TK5MBX15-06.exchange.corp.microsoft.com>

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. -- BillReceived on Tuesday, 23 June 2015 18:59:13 UTC

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