>>>>> "Seth" == Seth Falcon <[EMAIL PROTECTED]>
>>>>> on Thu, 18 May 2006 12:22:36 -0700 writes:
Seth> Ross Boylan <[EMAIL PROTECTED]> writes:
>> Is there any good source of information on how S4 classes (and methods)
>> work from C?
Hmm, yes; there's nothing in the "Writing R Extensions" manual,
and there's not so much in the ``The Green Book''
(Chambers 1998), which is prominently cited by Doug Bates (and Saikat Debroy)
in the paper given at DSC 2003 (mentioned earlier in this
thread, http://www.ci.tuwien.ac.at/Conferences/DSC-2003/Drafts/BatesDebRoy.pdf )
>> E.g., for reading
>> how to read a slot value
GET_SLOT(); also SET_SLOT(), NEW_OBJECT(), MAKE_CLASS(), ...
>> how to invoke a method
Well, an S4 method is still an R function so that's partly
covered by "R-exts" -- something I may want to avoid, rather
call the C function that *underlies* the (R) S4 method...
>> how to test if you have an s4 object
{I'd usually do those tests in R code}
Seth> You might look at Bioconductor's Ruuid package. It does some of this
Seth> and is fairly small, so it is easy to see what is going on.
Seth> http://bioconductor.org/packages/1.8/bioc/html/Ruuid.html
Indeed,. And the package which lead to the paper has later
become 'lme4' the C code of which *currently* is in the 'Matrix'
package -- which is much larger than Ruuid, but I think still
contains a many interesting examples of using S4 classes from C.
Since Matrix development uses a publicly-readable subversion
archive, you can directly browse the code at
https://svn.R-project.org/R-packages/trunk/Matrix/ (but for
extensive browsing do download and unpack the released version
of from CRAN, e.g., the US mirror,
http://cran.us.r-project.org/src/contrib/Descriptions/Matrix.html )
Particularly look at the src/...Matrix.c files and their
R/...Matrix.R counterparts.
Martin
Seth> + seth
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