[Rd] surprisingly, S4 classes with a "dim" or "dimnames" slot are final (in the Java sense)

2017-06-05 Thread Hervé Pagès 

Hi,

It's nice to be able to define S4 classes with slots that correspond
to standard attributes:

  setClass("A1", slots=c(names="character"))
  setClass("A2", slots=c(dim="integer"))
  setClass("A3", slots=c(dimnames="list"))

By doing this, one gets a few methods for free:

  a1 <- new("A1", names=letters[1:3])
  names(a1) # "a" "b" "c"
  a2 <- new("A2", dim=4:3)
  nrow(a2)  # 4
  a3 <- new("A3", dimnames=list(NULL, letters[1:3]))
  colnames(a3)  # "a" "b" "c"

However, when it comes to subclassing, some of these slots cause
problems. I can extend A1:

  setClass("B1", contains="A1")

but trying to extend A2 or A3 produces an error (with a non-informative
message in the 1st case and a somewhat obscure one in the 2nd):

  setClass("B2", contains="A2")
  # Error in attr(prototype, slotName) <- attr(pri, slotName) :
  #   invalid first argument

  setClass("B3", contains="A3")
  # Error in attr(prototype, slotName) <- attr(pri, slotName) :
  #   'dimnames' applied to non-array

So it seems that the presence of a "dim" or "dimnames" slot prevents a
class from being extended. Is this expected? I couldn't find anything
in TFM about this. Sorry if I missed it.

Thanks,
H.

--
Hervé Pagès

Program in Computational Biology
Division of Public Health Sciences
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N, M1-B514
P.O. Box 19024
Seattle, WA 98109-1024

E-mail: hpa...@fredhutch.org
Phone:  (206) 667-5791
Fax:(206) 667-1319

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[Rd] Usage of PROTECT_WITH_INDEX in R-exts

2017-06-05 Thread Kirill Müller 

Hi


I've noted a minor inconsistency in the documentation: Current R-exts reads

s = PROTECT_WITH_INDEX(eval(OS->R_fcall, OS->R_env), &ipx);

but I believe it has to be

PROTECT_WITH_INDEX(s = eval(OS->R_fcall, OS->R_env), &ipx);

because PROTECT_WITH_INDEX() returns void.


Best regards

Kirill

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