bug#16216: 24.3.50; <control> entries in `ucs-names'

[Eli Zaretskii]

> Date: Sat, 21 Dec 2013 21:08:35 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: 16216@debbugs.gnu.org
> 
> > Look at UnicodeData.txt, near the beginning of the file.
> 
> I see; thanks.  And I recall now that you pointed me to that
> file once before.
> 
> Still, that does not really answer the questions I posed, AFAICT.
> At least not for a user of `ucs-names' or the other functions
> mentioned.

I looked deeper and decided that this was a bug.  The Unicode Standard
explicitly says that control characters have no 'name' property (see
Section 4.8 in the Standard), and that those "<control>" things are
just labels.  The 'name' property cannot have lower-case characters of
"<>" in it anyway.

So starting with trunk revision 115693, all control characters will
have nil as their 'name' property, and "C-x 8 RET < TAB" will say "No
match".  (Some of the control characters have 'old-name' property, so
they still can be called out by name.)

> If `ucs-names' essentially corresponds to UnicodeData.txt, how
> about citing that in its doc?

The exact file is an implementation detail (there's a corresponding
XML file, which could be used if we wanted); the ELisp manual
documents that the properties are derived from UCD, the Unicode
Character Database.

Thanks.