Re: [Rd] Sweave processes \Sexpr in commented LaTeX source (2.3.1patched and 2.4.0)

From: Peter Dalgaard <p.dalgaard_at_biostat.ku.dk>
Date: Wed 20 Sep 2006 - 10:20:09 GMT

Friedrich Leisch <friedrich.leisch@stat.uni-muenchen.de> writes:

> >>>>> On Tue, 19 Sep 2006 19:14:39 -0500,
> >>>>> Marc Schwartz (MS) wrote:
>
> > Hi all,
> > On FC5, using:
>
> > Version 2.3.1 Patched (2006-08-06 r38829)
>
> > and today's
>
> > R version 2.4.0 alpha (2006-09-19 r39397)
>
> > with the following .Rnw file:
>
>
> > \documentclass[10pt]{article}
> > \begin{document}
>
> > This line should print '2': \Sexpr{1 + 1}
> > %% This line should NOT print '2': \Sexpr{1 + 1}
>
> > \end{document}
>
>
> > The \Sexpr in the second line is processed even though the line is
> > commented. This results in the following .tex file content (in the case
> > of R 2.4.0):
>
>
> > \documentclass[10pt]{article}
> > \usepackage{/home/marcs/R.Files/SourceCode/R-alpha/share/texmf/Sweave}
> > \begin{document}
>
> > This line should print '2': 2
> > %% This line should NOT print '2': 2
>
> > \end{document}
>
>
>
> > Shouldn't Sweave just generally ignore commented LaTeX code? In
> > reviewing Sweave.R I did not see a check for this, so perhaps there are
> > circumstances where one wants a \Sexpr in commented LaTeX code
> > processed. An example escapes me at the moment however.
>
> Sweave does not parse the LaTeX part of the document at all (which
> makes it a lot easier), all it does is looking for its own "magic
> strings" and replacing those, wherever they might occur.
>
> If we would start to respect comments, we would need a some kind of
> parser for LaTeX, which we currently don't need ... and starting to
> parse LaTeX would also open a can of worms of possible requests (what
> to do with Sexpr inside verbatim, etc, etc).

..not to mention TeX comments inside Sexpr (e.g. %*%...). Skipping lines with % as the first character might be a viable compromise though.

-- 
   O__  ---- Peter Dalgaard             ōster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)                  FAX: (+45) 35327907

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