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* can't be both non-capturing and still capture
@ 2017-07-03 20:47 srn@coolheads.com
2017-07-04 02:10 ` Re: can't be both non-capturing and still capture Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 1 reply; 2+ messages in thread
From: srn@coolheads.com @ 2017-07-03 20:47 UTC (permalink / raw)
To: pgsql-docs
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/9.6/static/index.html
Description:
In postgresql-doc-9.5/html/functions-matching.html#POSIX-MATCHING-RULES:
<PRE
CLASS="SCREEN"
>SELECT regexp_matches('abc01234xyz', '(?:(.*?)(\d+)(.*)){1,1}');
<I
CLASS="LINEANNOTATION"
>Result: </I
><SAMP
CLASS="COMPUTEROUTPUT"
>{abc,01234,xyz}</SAMP
></PRE
>
Here, the whole regexp is non-capturing, right, so how can the result be
reported as shown?
The previous two warmup examples do not have the surrounding
non-capturing-group markup. Looks to me like that markup should not appear
here, either.
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* Re: can't be both non-capturing and still capture
2017-07-03 20:47 can't be both non-capturing and still capture srn@coolheads.com
@ 2017-07-04 02:10 ` Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 0 replies; 2+ messages in thread
From: Tom Lane @ 2017-07-04 02:10 UTC (permalink / raw)
To: srn@coolheads.com; +Cc: pgsql-docs
srn@coolheads.com writes:
> Here, the whole regexp is non-capturing, right, so how can the result be
> reported as shown?
No, the outer parens are non-capturing, but the ones inside them still
are capturing parens.
Perhaps it would clarify matters if you tried it with plain outer parens:
=# SELECT regexp_matches('abc01234xyz', '((.*?)(\d+)(.*)){1,1}');
regexp_matches
-----------------------------
{abc01234xyz,abc,01234,xyz}
(1 row)
In this case we get a report from each of the four sets of capturing
parens. Or another example:
=# SELECT regexp_matches('abc01234xyz', '((?:.*?)(\d+)(.*)){1,1}');
regexp_matches
-------------------------
{abc01234xyz,01234,xyz}
(1 row)
Outer parens capture, first inner set don't, other two inner sets do.
regards, tom lane
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2017-07-03 20:47 can't be both non-capturing and still capture srn@coolheads.com
2017-07-04 02:10 ` Tom Lane <tgl@sss.pgh.pa.us>
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