From: Kenichi Handa <handa@m17n.org>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: 9653@debbugs.gnu.org
Subject: bug#9653: 24.0.50; `ucs-names' - Why all of the ("" . XXX) entries?
Date: Tue, 04 Oct 2011 10:59:55 +0900 [thread overview]
Message-ID: <tl7ehytwm78.fsf@m17n.org> (raw)
In-Reply-To: <jwvd3eep5vo.fsf-monnier+emacs@gnu.org> (message from Stefan Monnier on Mon, 03 Oct 2011 09:31:29 -0400)
In article <jwvd3eep5vo.fsf-monnier+emacs@gnu.org>, Stefan Monnier <monnier@iro.umontreal.ca> writes:
> > * For miscellaneous properties which take strings as
> > values, such as the Unicode Name property, the default
> > value is a null string.
> > ^^^^^^^^^^^^^
> I'm not opposed to this change, but your answer surprises me:
> - we don't have to follow any standard.
But, it is better to follow a standard, especially an
important one as Unicode.
> - even less so when it talks about internal APIs rather than about
> externally-visible behavior.
I think that UCD is talking about external visible
behaviour. Unicode says that all characters have `Name'
property and each value is a string. So, when you ask a
name of a specific character, you should always get a string
value.
> - "null string" can mean nil just as well as it can mean "".
But, as I wrote, nil usually means
no-value/not-specified/unassigned/unknown, which is
different from the explicit "".
> They actually behave quite similarly: length/concat/mapcar treat them
> the same, aref signals an error in both cases, ...
Similar but different. I think the difference is bigger.
insert/string-match/search-forward/etc. signal an error on
nil argument.
And these two signals the different error; wrong-type-argument
vs. args-out-of-range.
(aref nil 1)
(aref "" 1)
> So was there some other motivation (e.g. simpler implementation?
No.
> Simpler code somewhere else?)?
Yes, hypothetically. You can safely write, for instance,
(search-forward (get-char-code-property CHAR 'name) ...)
or
(insert (get-char-code-property CHAR 'name) ...)
without checking the return value.
> If not (i.e. all things being equal) I'd
> prefer to use nil which is ever so slightly closer to usual Elisp
> practice,
Really? I've thought nil and "" are rather different object
in Elisp. In a char-table, (aset CHAR-TABLE CHAR nil)
results in that (aref CHAR-TABLE CHAR) returns the default
value which may not be nil.
> and matches the Emacs-23 behavior.
I'm sorry for this incomaptible change. As I wrote before,
when I first implemented UCD in Emacs, the Unicode was not
clear about the property value of a character not explicitly
listed in the database file. So, at that time, I simply
selected nil as the default value. But, recently I found
that the default value is clearly defined in the recent
versions of Unicode.
So, if you the emacs maintainer thinks that the backward
compatibility is more important, I don't oppose to change
the default value back to nil.
---
Kenichi Handa
handa@m17n.org
next prev parent reply other threads:[~2011-10-04 1:59 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <<74B14D2A03144E798C9415172D5FE01A@us.oracle.com>
[not found] ` <<tl7fwe65odg.fsf@m17n.org>
2011-10-02 16:36 ` bug#9653: 24.0.50; `ucs-names' - Why all of the ("" . XXX) entries? Drew Adams
2011-10-02 17:38 ` Drew Adams
2011-10-02 22:31 ` Juanma Barranquero
2011-10-02 22:51 ` Drew Adams
2011-10-02 22:55 ` Juanma Barranquero
2011-10-03 13:20 ` Jason Rumney
2011-10-03 13:56 ` Drew Adams
2011-10-03 14:00 ` Juanma Barranquero
2011-10-02 18:09 ` Thierry Volpiatto
2011-10-03 1:28 ` Stefan Monnier
2011-10-03 4:23 ` Kenichi Handa
2011-10-03 8:22 ` Andreas Schwab
2011-10-04 1:14 ` Kenichi Handa
2011-10-03 13:31 ` Stefan Monnier
2011-10-04 1:59 ` Kenichi Handa [this message]
2011-10-04 12:56 ` Stefan Monnier
2011-10-06 3:53 ` Kevin Rodgers
2011-10-06 12:19 ` Juanma Barranquero
2011-10-06 13:02 ` Andreas Schwab
2011-10-06 13:47 ` Juanma Barranquero
2011-10-06 14:01 ` Andreas Schwab
2011-10-06 14:02 ` Juanma Barranquero
2011-10-04 2:19 ` Drew Adams
2011-10-04 4:02 ` Kenichi Handa
2011-10-04 13:43 ` Drew Adams
2011-10-04 17:34 ` Drew Adams
2011-10-04 18:19 ` Eli Zaretskii
2011-10-04 18:30 ` Drew Adams
2011-10-04 20:55 ` Eli Zaretskii
2011-10-04 21:39 ` Stefan Monnier
2011-10-04 22:03 ` Drew Adams
2011-10-05 4:11 ` Eli Zaretskii
2011-10-05 13:20 ` Drew Adams
2011-10-05 17:24 ` Eli Zaretskii
2011-10-05 8:59 ` Kenichi Handa
2011-10-05 10:20 ` Eli Zaretskii
2011-10-05 12:40 ` Stefan Monnier
2011-10-06 18:02 ` Eli Zaretskii
2011-10-06 20:56 ` Stefan Monnier
2012-01-14 18:35 ` Drew Adams
2012-02-17 15:55 ` Drew Adams
2018-02-13 23:35 ` Drew Adams
2018-02-15 1:11 ` Noam Postavsky
2018-02-15 3:17 ` Drew Adams
[not found] <tl74nupdi7g.fsf@m17n.org>
2012-02-17 15:25 ` Stefan Monnier
[not found] ` <7CCDEE21B0ED42B097600BB24692952A@us.oracle.com>
2012-02-17 23:42 ` Stefan Monnier
2012-02-18 0:05 ` Drew Adams
[not found] ` <8339a8wp2m.fsf@gnu.org>
2012-02-18 19:08 ` Drew Adams
2012-02-20 0:39 ` Kenichi Handa
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