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2019-05-20 cf92226e9f Doc: improve description of regexp character classes.
* Character classes
@ 2019-05-20 16:37 PG Doc comments form <noreply@postgresql.org>
0 siblings, 1 reply; 3+ messages in thread
From: PG Doc comments form @ 2019-05-20 16:37 UTC (permalink / raw)
To: pgsql-docs@lists.postgresql.org; +Cc: geert.lobbestael@gmail.com
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/11/functions-matching.html
Description:
On https://www.postgresql.org/docs/11/functions-matching.html paragraph
9.7.3.2. Bracket Expressions says "Standard character class names are:
alnum, alpha, blank, cntrl, digit, graph, lower, print, punct, space, upper,
xdigit". The class "ascii" exists, but is not mentioned (probably a
combination of some of the other classes). Are there any other classes? Do
they work only for ASCII characters (e.g. '\u00A0' is not picked up by
'[:blank:]')?
best regards
geert
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: Character classes
@ 2019-05-20 18:06 Tom Lane <tgl@sss.pgh.pa.us>
parent: PG Doc comments form <noreply@postgresql.org>
0 siblings, 1 reply; 3+ messages in thread
From: Tom Lane @ 2019-05-20 18:06 UTC (permalink / raw)
To: geert.lobbestael@gmail.com; +Cc: pgsql-docs@lists.postgresql.org
PG Doc comments form <noreply@postgresql.org> writes:
> On https://www.postgresql.org/docs/11/functions-matching.html paragraph
> 9.7.3.2. Bracket Expressions says "Standard character class names are:
> alnum, alpha, blank, cntrl, digit, graph, lower, print, punct, space, upper,
> xdigit". The class "ascii" exists, but is not mentioned (probably a
> combination of some of the other classes). Are there any other classes?
Hm, fair question. I think the text means to say that these are the
character class names required by the POSIX regexp spec, which is
accurate. A look into our src/backend/regex/regc_locale.c will show
you that we also implement "ascii", and no others. That probably ought
to be documented.
> Do they work only for ASCII characters (e.g. '\u00A0' is not picked up
> by '[:blank:]')?
The POSIX ones are implemented by calling the C library, so it's whatever
the ctype.h and wctype.h functions think is appropriate for your LC_CTYPE
setting.
The 20-year-old reference in our text to ctype(3) seems rather unhelpful
today; in the first place, there's no such man page on my Linux systems,
and in the second place, wctype(3) is more important if it exists, and
in the third place what a reader actually wants to know is that this
is controlled by the LC_CTYPE server parameter. It'd likely be better
to dump the man-page reference altogether and instead point readers to
our "Locale Support" chapter.
regards, tom lane
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: Character classes
@ 2019-05-21 09:18 Thomas Munro <thomas.munro@gmail.com>
parent: Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 0 replies; 3+ messages in thread
From: Thomas Munro @ 2019-05-21 09:18 UTC (permalink / raw)
To: Tom Lane <tgl@sss.pgh.pa.us>; +Cc: geert.lobbestael@gmail.com; pgsql-docs@lists.postgresql.org
On Tue, May 21, 2019 at 6:06 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> The 20-year-old reference in our text to ctype(3) seems rather unhelpful
> today; in the first place, there's no such man page on my Linux systems,
> and in the second place, wctype(3) is more important if it exists, and
> in the third place what a reader actually wants to know is that this
> is controlled by the LC_CTYPE server parameter. It'd likely be better
> to dump the man-page reference altogether and instead point readers to
> our "Locale Support" chapter.
No opinion on the reference, but out of curiosity I hunted down the
equivalent man page on a RHEL system. There it goes by ctype.h(0P),
which makes some kind of sense: there isn't a ctype function, so it
has no business in section 3, while wctype is a function so there is a
wctype(3) along with a header page wctype.h(0P). 0P seems to be for
POSIX headers, or something like that. BSDen don't seem to bother
with this distinction and just provide ctype(3).
--
Thomas Munro
https://enterprisedb.com
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2019-05-20 18:06 ` Tom Lane <tgl@sss.pgh.pa.us>
2019-05-21 09:18 ` Thomas Munro <thomas.munro@gmail.com>
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