Re: DB2 regex bug with look around ?

Hi John,

I have used it quite a lot for other things, I just recently noticed this
anomaly.

In general it returns null for a failed match or sqlcode < 0 if the regex
is invalid.

You don't need parentheses for capturing text - and the whole regex has to
match for a success.

Given it didn't return null or an error, it thinks it matched ( which you
can also see using regexp_count = 1, but if it matched it should have a
digit in the matched text, hence my confusion.

If it couldn't find a digit, or did find a digit but it had an 'a' on one
or both sides, it should fail or else it should report a match and the
matched text should include the digit matched by the regex.

If you apply \w+(?!$)
To a2B

For example,

You get returned a2

The greedy w+ has to "give up" the B because the look ahead for "not at end
of line" fails

Anyway, it's no biggie but it does look like a bug to me

On Thursday, 28 April 2016, John Yeung <gallium.arsenide@xxxxxxxxx> wrote:

On Thu, Apr 28, 2016 at 5:58 AM, Craig Richards <craig@xxxxxxxxxxxxxxxx
<javascript:;>> wrote:

If you check the regex and the string it's applied to, and ignore my

typos

( sorry ) I think you'll find it doesn't select the correct matched text

(

or else my understanding is wrong )

Well, we don't have a high enough TR on our 7.1 system for me to test
this directly, but I tried it in Python, which I think should behave
the same in this case.

The search may not be returning anything other than success or failure
unless you have something to capture. It's telling you it found the
pattern, but that's all. To return the digit, try surrounding the \d
in parens:

'(?<!a)(\d)(?!a)'

John Y.
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