[R] Contributing to the R Extensions documentation

Ross Boylan ross at biostat.ucsf.edu
Wed Nov 5 21:31:28 CET 2003

On Wed, 2003-11-05 at 12:06, Prof Brian Ripley wrote:
> A list is just a vector of type VECSXP.
> There IS a section called `Handling lists'.
> I don't think the gap is in the `Writing R Extensions' document, maybe in 
> your reading of it.
That section discusses reading lists, not making them.

It also includes no explicit statement that the names of list items are
in the R_NamesSymbol attribute, nor instructions on how to create the
value that goes in that attribute (i.e., it should be a character vector
and its elements made with mkChar()).  (I'm also not sure how deep one
needs to use PROTECT, though that's a more general issue.)

There is no explicit statement that the elements of the list are
arbitrary SEXP's.

I also had the list[i] vs list[[i]] lurking in my mind, wondering how
that mapped to the C level constructs.  That is less central.

I'm not saying the clues aren't there; after all, I did work it out, I
think correctly.  I am saying that certain information would be better
stated explicitly rather than simply being open to inference from an
example.  And I am saying that an explicit example of constructing and
returning a list (with named members) would be useful, since that's a
common scenario.

> On Wed, 5 Nov 2003, Ross Boylan wrote:
> > I thought there were some gaps in the R Extensions document; in
> > particular, I was left wondering how to create a list.  I think a
> > paragraph on it would be useful.
> > 
> > I would be happy to contribute the paragraph, but I'm not sure if
> > there's interest or what the procedure is.  Can anyone advise me?
> > 
> > Though I was looking at the 1.7.0 version, I just checked 1.8.0 and the
> > relevant section seems the same.
> > 
> > My ulterior motive is to discover if my understanding of lists is
> > actually correct :)
> > 
Ross Boylan                                      wk:  (415) 502-4031
530 Parnassus Avenue (Library) rm 115-4          ross at biostat.ucsf.edu
Dept of Epidemiology and Biostatistics           fax: (415) 476-9856
University of California, San Francisco
San Francisco, CA 94143-0840                     hm:  (415) 550-1062

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