Ross == Ross Boylan [EMAIL PROTECTED]
on Wed, 05 Nov 2003 12:31:28 -0800 writes:
Ross 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.
Ross That section discusses reading lists, not making them.
Ross It also includes no explicit statement that the names
Ross of list items are in the R_NamesSymbol attribute, nor
Ross instructions on how to create the value that goes in
Ross that attribute (i.e., it should be a character vector
Ross and its elements made with mkChar()). (I'm also not
Ross sure how deep one needs to use PROTECT, though that's
Ross a more general issue.)
Ross There is no explicit statement that the elements of
Ross the list are arbitrary SEXP's.
Ross I also had the list[i] vs list[[i]] lurking in my
Ross mind, wondering how that mapped to the C level
Ross constructs. That is less central.
Ross I'm not saying the clues aren't there; after all, I
Ross did work it out, I think correctly. I am saying that
Ross certain information would be better stated explicitly
Ross rather than simply being open to inference from an
Ross example. And I am saying that an explicit example of
Ross constructing and returning a list (with named members)
Ross would be useful, since that's a common scenario.
I tend to agree.
I assume most people will read that manual electronically --- as
opposed to on paper, because you can search quickly ---
and such a proposed addition would be quite helpful.
Alternatively, and sometimes even more usefully,
one could consider providing these more extended examples as
files (*.c, *.R, Makefile, .. or even better, as an R package
(with a vignette !) which would have an almost purely didactical
aim. As an R package --- source only, no binaries! --- it had
the advantage of providing provably (via R CMD check) working
code.
Martin Maechler [EMAIL PROTECTED] http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum LEO C16Leonhardstr. 27
ETH (Federal Inst. Technology) 8092 Zurich SWITZERLAND
phone: x-41-1-632-3408 fax: ...-1228
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 :)
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