Hi all,
Not sure if this belongs to R-devel or R-package-devel. Anyways...
Suppose we have objects of class c("foo", "bar"), and there
are two S3
methods c.foo, c.bar. In c.foo, I'm trying to modify the dots and
forward the dispatch using NextMethod without any success. This is
what I've tried so far:
c.foo <- function(..., recursive=FALSE) {
dots <- list(...)
# inspect and modify dots
# ...
do.call(
function(..., recursive=FALSE) structure(NextMethod("c"),
class="foo"),
c(dots, recursive=recursive)
)
}
foobar <- 1
class(foobar) <- c("foo", "bar")
c(foobar, foobar)
Error: C stack usage 7970788 is too close to the limit
There's recursion (!). But the funniest thing is that if c.foo is
exported by one package and c.bar is exported by another one, there's
no recursion, but c.bar is never called (!!). Why is the same code
behaving in a different way depending on whether these functions are
defined in the .GlobalEnv or in two attached packages? (BTW,
isS3method() is TRUE, for c.foo and c.bar in both cases).
I'm blocked here. Am I missing something? Is there a way of doing
this? Thanks in advance.
Regards,
I?aki
I've set up a repo with a reproducible example of the issue described in my last email: https://github.com/Enchufa2/dispatchS3dots I?aki 2018-02-20 19:33 GMT+01:00 I?aki ?car <i.ucar86 at gmail.com>:> Hi all, > > Not sure if this belongs to R-devel or R-package-devel. Anyways... > > Suppose we have objects of class c("foo", "bar"), and there are two S3 > methods c.foo, c.bar. In c.foo, I'm trying to modify the dots and > forward the dispatch using NextMethod without any success. This is > what I've tried so far: > > c.foo <- function(..., recursive=FALSE) { > dots <- list(...) > # inspect and modify dots > # ... > do.call( > function(..., recursive=FALSE) structure(NextMethod("c"), class="foo"), > c(dots, recursive=recursive) > ) > } > > foobar <- 1 > class(foobar) <- c("foo", "bar") > c(foobar, foobar) > Error: C stack usage 7970788 is too close to the limit > > There's recursion (!). But the funniest thing is that if c.foo is > exported by one package and c.bar is exported by another one, there's > no recursion, but c.bar is never called (!!). Why is the same code > behaving in a different way depending on whether these functions are > defined in the .GlobalEnv or in two attached packages? (BTW, > isS3method() is TRUE, for c.foo and c.bar in both cases). > > I'm blocked here. Am I missing something? Is there a way of doing > this? Thanks in advance. > > Regards, > I?aki-- I?aki ?car http://www.enchufa2.es @Enchufa2
The example is invoking NextMethod via an anonymous function, which is not allowed (see documentation for NextMethod). Normally one gets a runtime error "'NextMethod' called from an anonymous function", but not here as the anonymous function is called via do.call. I will fix so that there is a runtime error in this case as well, thanks for uncovering this problem. I don't think there is a way to replace (unnamed) arguments in dots for NextMethod. Tomas On 02/21/2018 02:16 PM, I?aki ?car wrote:> I've set up a repo with a reproducible example of the issue described > in my last email: > > https://github.com/Enchufa2/dispatchS3dots > > I?aki > > 2018-02-20 19:33 GMT+01:00 I?aki ?car <i.ucar86 at gmail.com>: >> Hi all, >> >> Not sure if this belongs to R-devel or R-package-devel. Anyways... >> >> Suppose we have objects of class c("foo", "bar"), and there are two S3 >> methods c.foo, c.bar. In c.foo, I'm trying to modify the dots and >> forward the dispatch using NextMethod without any success. This is >> what I've tried so far: >> >> c.foo <- function(..., recursive=FALSE) { >> dots <- list(...) >> # inspect and modify dots >> # ... >> do.call( >> function(..., recursive=FALSE) structure(NextMethod("c"), class="foo"), >> c(dots, recursive=recursive) >> ) >> } >> >> foobar <- 1 >> class(foobar) <- c("foo", "bar") >> c(foobar, foobar) >> Error: C stack usage 7970788 is too close to the limit >> >> There's recursion (!). But the funniest thing is that if c.foo is >> exported by one package and c.bar is exported by another one, there's >> no recursion, but c.bar is never called (!!). Why is the same code >> behaving in a different way depending on whether these functions are >> defined in the .GlobalEnv or in two attached packages? (BTW, >> isS3method() is TRUE, for c.foo and c.bar in both cases). >> >> I'm blocked here. Am I missing something? Is there a way of doing >> this? Thanks in advance. >> >> Regards, >> I?aki > >