I love Sweave

petris-style.Rnw

\documentclass{article}

\DefineVerbatimEnvironment{Sinput}{Verbatim}{xleftmargin=2em,
 fontsize=\footnotesize, fontshape=sl}
\DefineVerbatimEnvironment{Soutput}{Verbatim}{xleftmargin=2em,
 fontsize=\footnotesize}
\fvset{listparameters={\setlength{\topsep}{0pt}}}
\renewenvironment{Schunk}{\vspace{\topsep}}{\vspace{\topsep}}

\begin{document}

<<setup, include=FALSE>>=
render_sweave()
@

The quick brown fox jumps over the lazy dog the quick brown fox jumps over the
lazy dog the quick brown fox jumps over the lazy dog.

<<test>>=
1+1
rnorm(30)
@

The quick brown fox jumps over the lazy dog the quick brown fox jumps over the
lazy dog the quick brown fox jumps over the lazy dog.

\end{document}

sweave-knitr.Rnw

\documentclass{article}
\usepackage{Sweave}
\begin{document}

This is how knitr looks like:

<<knitr-block, foo=render_latex()>>=
1+1
rnorm(5)
@

This is how Sweave looks like:

<<sweave-block, foo=render_sweave()>>=
<<knitr-block>>
@

<<setup-preamble, include=FALSE>>=
render_latex()
set_header(highlight = knitr:::.header.hi.tex)
@

\end{document}