Pb with lapply()

Hi,

If needed, lapply() tries to convert its first argument into a list
before it starts doing something with it:

 > lapply

 function (X, FUN, ...)
 {
   FUN <- match.fun(FUN)
   if (!is.vector(X) || is.object(X))
       X <- as.list(X)
   .Internal(lapply(X, FUN))
 }

But in practice, things don't always seem to "work" as suggested by
this code (at least to the eyes of a naive user).

I have defined an "as.list" method for my S4 class "A":

 > setClass("A", representation(data="list"))

 [1] "A"

 > setMethod("as.list", "A", function(x, ...) x at data)

 Creating a new generic function for "as.list" in ".GlobalEnv"
 [1] "as.list"

Testing it:

 > a <- new("A", data=list(8, 2:0))
 > as.list(a)

 [[1]]
 [1] 8

 [[2]]
 [1] 2 1 0

OK.

But lapply() doesn't work on 'a':

 > lapply(a, typeof)

 Error in as.vector(x, "list") : cannot type 'S4' coerce to vector

I still have to do the 'as.list(a)' part myself for things to work:

 > lapply(as.list(a), typeof)

 [[1]]
 [1] "double"

 [[2]]
 [1] "integer"

Seems like using force() inside lapply() would solve the problem:

 lapply2 <- function(X, FUN, ...)
 {
   FUN <- match.fun(FUN)
   if (!is.vector(X) || is.object(X))
       X <- force(as.list(X))
   .Internal(lapply(X, FUN))
 }

It works now:

 > lapply2(a, typeof)

 [[1]]
 [1] "double"

 [[2]]
 [1] "integer"

Cheers,
H.