RE using a variable within a regexp pattern

[Manuel Souto Pico]

Dear David and Hans-Juergen,

Thanks a lot for your replies and, notably, for Jans-Juergen's explanation.
Very useful indeed!

This is a bit more complex than perl's regular expressions but still quite
straightforward at the end of the day. The solution had crossed my mind very
fast, but then I got distracted and I forgot. But indeed this is what I
needed:

        where $record/langSet[@xml:lang="en"]/tig/term[matches(.,
concat('^', $q, '.*$'))]

Thanks a lot! And keep well :))
Chees, Manuel


2009/10/1 Hans-Juergen Rennau <http://x-query.com/mailman/listinfo/talk>

> Hi Manual,
>
> if I understand you correctly, you wonder how you can compose a match
> pattern from variable and fixed  parts, e.g. framing a variable term by an
> initial ^ and a trailing $, right?
>
> The solution is simple: use an _expression_ whose string value is the
> desired sequence of characters. Often this will be achieved using the concat
> function, whose arguments in turn may be literals, variable references,
> function calls, path expressions.... Examples:
>
> matches(., concat('^', $q, '$'))
> matches(., concat($prefix, $q, $postfix))
> matches(., concat('^', 'ID', position()))
> matches(., concat('^', $n/@criterion, '.*s'))
>
> So the task becomes very simple if you remember that the way an expression
> is resolved to a value is independent on the context where the value is
> used. Therefore, you need not any special knowledge about the matches
> function - all you need is the general understanding how to build an
> expression that resolves to the intended string.
>
> With kind regards,
> Hans-Juergen
>
> ------------------------------
>
> Message: 4
> Date: Thu, 1 Oct 2009 20:53:29 +0200
> From: Manuel Souto Pico <http://x-query.com/mailman/listinfo/talk>
> Subject:  using a variable within a regexp pattern in
>    XQuery
> To: http://x-query.com/mailman/listinfo/talk
> Message-ID:
>    <http://x-query.com/mailman/listinfo/talk>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Hi,
>
> I'm a bit stuck trying to run a regexp pattern in a XQuery search file.
>
> (1) where $record/langSet[@xml:lang="en"]/tig/term[matches(., $q)]
> works
> (2) where $record/langSet[@xml:lang="en"]/tig/term[matches(.,
> "$q")]            doesn't work
> (3) where $record/langSet[@xml:lang="en"]/tig/term[matches(.,
> "^$q.*$")]         doesn't work
> (4) where $record/langSet[@xml:lang="en"]/tig/term[matches(.,
> "^bu.+$")]          works!
>
> Any ideas about how I can get to use regular expressions in this query?
>
> (4) retrieves 'bufer', 'bug' and 'bus'. If $q is 'bu', (1) retrieves as
> well
> 'attri*bu*te', 'contrast *bu*tton', etc.
>
> Thanks a lot!
>
> Cheers, Manuel
>
>
>
>
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