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Re: [Fwd: SPARQL: Backslashes in string literals]

From: Eric Prud'hommeaux <eric@w3.org>
Date: Fri, 5 Aug 2005 15:28:03 -0400
To: Dave Beckett <dave.beckett@bristol.ac.uk>
Cc: Andy Seaborne <andy.seaborne@hp.com>, Steve Harris <S.W.Harris@ecs.soton.ac.uk>, RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-ID: <20050805192803.GA3162@w3.org>
On Fri, Aug 05, 2005 at 11:37:20AM +0100, Dave Beckett wrote:
> 
> On Fri, 2005-08-05 at 10:03 +0100, Steve Harris wrote:
> > On Thu, Aug 04, 2005 at 04:56:17 +0100, Andy Seaborne wrote:
> > > >so charmod says this should work:
> > > >
> > > > SELECT ?foo\x0045bar WHERE { ?foo\x0045bar dc:title ?xyz }.
> > > 
> > > We can do one of:
> > > 1/ Extend \u and \U to apply to variables
> > > 2/ Make it so \u is on input processing (before tokenizing)
> > >    so it works everywhere including comments and is transparent to
> > >    parsing proper
> > > 
> > > 1/ is probable clearer 2/ is probably easier to implement
> 
> 2/ is way harder to implement for me.  The lexer and parser I've been
> using do not work on unicode code points so adding an extra layer in
> there will substantially complicate things.  I will likely ignore 2/ for
> some time if it was chosen and mark any tests for it as will-not-pass.
> 
> > > A test is "SELEC\u0054"
> > > 
> > > Another is the comment
> > > 
> > >     # \u escapes need thinking about.
> > > 
> > > which is illegal by 2 but legal by 1.
> > 
> > Unless comment processing is also done on input (ala the C pre-processor)
> > I dont know if I like the idea of
> > 	/* comment \u002A/
> > being a valid comment
> 
> Since comments have no in-language interpretation, they can include any
> printable byte that matches the grammar.  If utf8 items or \uxxx are in
> comments, software doesn't care.

I think Steve meant that one of the comment boundries was formed by
the escape sequence. For example:
  SELECT * # get it all\nWHERE {?x\u0020foo:bar\u0020?y}

(un-escapes to:
  SELECT * # get it all
WHERE {?x foo:bar ?y}

This would be a possible side effect of taking Andy's option 2 (if escape
expansion is done prior to, rather than during tokenizing).
-- 
-eric

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Received on Friday, 5 August 2005 19:28:06 GMT

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