Sweave processes \Sexpr in commented LaTeX source (2.3.1patched and 2.4.0)

Peter Dalgaard <p.dalgaard at biostat.ku.dk> writes:

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

+1.  You could probably ignore any lines where the first
non-whitespace char is '%'.  But if that seems to risky, then only
recognizing first-char-is-% seems a worthwhile heuristic.

Another place where this has bitten people is when they do:

%\usepackage{Sweave}

Sweave picks that up and doesn't insert the usepackage line itself.
So ignoring LaTeX comment lines would solve two problems.

Best,

+ seth