XQuery - RegEx Pattern Matcher

[Michael Kay]

These things tend to be easier in XSLT which has the more powerful
xsl:analyze-string instruction.

<xsl:analyze-string regex='"[^"]*?"|[^;]*'>
  <xsl:matching-substring>
    .. process one field ..


In XQuery think I would start by doing a replace() to replace
semicolons-not-within-quotes by some other delimiter (e.g. a PUA character),
and then do a tokenize() to split the string on this new delimiter.

Alternatively, splitting the string using a recursive function using
substring-before() and substring-after() might be just as easy.

Regards,

Michael Kay
http://www.saxonica.com/
http://twitter.com/michaelhkay 


> -----Original Message-----
> From: http://x-query.com/mailman/listinfo/talk [mailto:http://x-query.com/mailman/listinfo/talk] 
> Sent: 19 June 2009 11:29
> To: Michael Kay; http://x-query.com/mailman/listinfo/talk
> Subject: Re: RE:  XQuery - RegEx Pattern Matcher
> 
> I am trying to "read" CSV data like this :
> 
> one;"two;stilltwo";three;"four;stillfour";five
> 
> this should resolve in something like this :
> ...
> <element>one</element>
> <element>two;stilltwo</element>
> <element>three</element>
> <element>four;stillfour</element>
> <element>five</element>
> ...
> 
> if there is no separator(";") allowed within a text it is 
> easy with just splitting a line with ";".
> 
> But if there can be a ";" as a text, than I have to use RegEx.
> I succeded in finding a XQuery-RegEx if in one line there is 
> only one case where a ";" is used as text.
> 
> But I need to find every match, so I used the \\G . Worked 
> fine, so I hoped to reuse it in XQuery...
> 
> 
> 
> -------- Original-Nachricht --------
> > Datum: Fri, 19 Jun 2009 10:20:30 +0100
> > Von: "Michael Kay" <http://x-query.com/mailman/listinfo/talk>
> > An: http://x-query.com/mailman/listinfo/talk, http://x-query.com/mailman/listinfo/talk
> > Betreff: RE:  XQuery - RegEx Pattern Matcher
> 
> > 
> > The XPath regular expression language does not recognize \G and it 
> > does not recognize non-capturing groups.
> > 
> > As far as matches() is concerned, there is no distinction between 
> > capturing and non-capturing groups, so replace "(?:" by "(".
> > 
> > I suspect you wanted your regex to contain "\G". In Java 
> you need to 
> > escape this as "\\G"; in XPath/XQuery, backslash is not a special 
> > character and does not need to be escaped. However, there's 
> no "\G" in 
> > XPath regular expressions anyway. In Java it means "the end of the 
> > previous match"; but XQuery is a functional language, so 
> "previous" is 
> > meaningless. At this stage I give up because I'm not sure 
> what you are 
> > trying to do: you haven't supplied enough of your code.
> > 
> > Regards,
> > 
> > Michael Kay
> > http://www.saxonica.com/
> > http://twitter.com/michaelhkay
> > 
> > > -----Original Message-----
> > > From: http://x-query.com/mailman/listinfo/talk
> > > [mailto:http://x-query.com/mailman/listinfo/talk] On Behalf Of http://x-query.com/mailman/listinfo/talk
> > > Sent: 19 June 2009 09:33
> > > To: http://x-query.com/mailman/listinfo/talk
> > > Subject:  XQuery - RegEx Pattern Matcher
> > > 
> > > Hi,
> > > I am trying to use a RegEx within XQuery. In general that 
> works fine.
> > > Now I have a more complex RegEx to work with CSV-files(these CSV 
> > > have ";" as separator).
> > > I use can the following without problems in Java :
> > > 
> > > Pattern Regex = Pattern.compile(
> > > "\\G(?:^|;)(?:\"((?:[^\"]|\"\")*)\"|([^\";]*))");
> > > ...
> > > 
> > > But in XQuery
> > > let $regularExpr :='\\G(?:^|;)(?:\"((?:[^\"]|\"\")*)\"|([^\";]*))'
> > > ...
> > > if (matches($row,$regularExpr) ) then ( ...
> > > 
> > > just gives the error :
> > > 
> > > Error at character 4 in regular expression
> > > "\\G(?:^|;)(?:\"((?:[^\"]|\"\")...": expected ())
> > > 
> > > 
> > > I tried the optional flags (i, x, ...) but always with the same 
> > > result...
> > > What is wrong with this RegEx ?
> > > 
> > > P.S. :I run the XQuery from Java with Saxon.
> > > 
> > > 
> > > --
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> > > http://x-query.com/mailman/listinfo/talk
> > 
> > 
> > _______________________________________________
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