[R] Summary (Re: (S|odf)weave : how to intersperse (\LaTeX{}|odf) comments in source code ? Delayed R evaluation ?)

[Gabor Grothendieck]

On Sun, Dec 12, 2010 at 6:30 PM, Emmanuel Charpentier
<emm.charpentier at free.fr> wrote:
> Dear list,
>
> see comment at end.
>
> On Sat, 11 Dec 2010 22:58:10 +0000, Emmanuel Charpentier wrote :
>
>> Dear list,
>>
>> Inspired by the original Knuth tools, and for paedaogical reasons, I
>> wish to produce a document presenting some source code with interspersed
>> comments in the source (see Knuth's books rendering TeX and metafont
>> sources to see what I mean).
>>
>> I seemed to remember that a code chunk could be defined piecewise, like
>> in
>>
>> Comments...
>>
>> <<Chunk1, eval=FALSE, echo=TRUE>>=
>> SomeCode
>> @
>>
>> Some other comments...
>>
>> <<Chunk2, eval=FALSE, echo=TRUE>>=
>> MoreCode
>> @
>>
>> And finally,
>>
>> <<Chunk3, eval=TRUE, echo=TRUE>>=
>> <<Chunk1>>
>> <<Chunk2>>
>> EndOfTheCode
>> @
>>
>> That works ... as long as SomeCode, MoreCode and EndOfTheCode are self-
>> standing pieces of R code, but *not* code fragments. You can *not*
>> intersperse comments in, say, a function body, or  local() environment
>> this way : when Sweaving, *R* complains of an incomplete source (makes
>> noise about an unexpected end of input at the end of Chunk1, IIRC, and
>> never sees Chunk2).
>>
>> I hoped that Sweave's "alternative" syntax could offer a way out : no
>> such luck.
>>
>> There seems to be no way to delay R evaluation of a R chunk passed by
>> Sweave ; at least, the "eval=FALSE" option of chunk declaration is not
>> sufficient for that.
>>
>> Am I missing something in the Sweave nd odfWeve documentations (that I
>> read till I grew green and moldy) ? Or does this require a fundamental
>> change in the relevant Sweave drivers ?
>>
>> Can you suggest alternative ways of doing what I mean to do ? The only
>> workaround I found is to paste a second copy of my code in a \verbatim
>> environment (or, in the case of odfWeave, in the "text" part), and spice
>> it with \end{verbatim} comments.. \begin{verbatim} chunks. This way, I
>> lose any guarantee of consistency between commented text and effective
>> code.
>>
>> Any other idea ?
>>
>>                                       Emmanuel Charpentier
>
>
> To summarize the answers I got so far, there seems to be no satisfactory
> solutions to my current problem with either Sweave or odfWeave :
>        - every (Sw|odfW)eave code chunk has to be parseable in itself.
> One cannot break it in unparseable pieces in home to paste it later ;
>        - the (hypothetical) "parse=FALSE" option, suggested by Duncan
> Murdoch, is, well, hypothetical ;
>        - the brew package is not integrated in either Sweave or
> odfWeave ;

brew doesn't need to be.  Its an alternative to Sweave, not something
intended to be used with Sweave.

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