Message-ID: <747cf507-e25b-d05f-366d-7f1ea2ddcbcd@gmail.com>
Date: 2019-07-15T12:16:57Z
From: Duncan Murdoch
Subject: Possible bug in `class<-` when a class-specific '[[.' method is defined
In-Reply-To: <1be44ffeed8e46619c57a9f8fae974b6@epfl.ch>
On 07/07/2019 11:49 a.m., Ghiggi Gionata wrote:
> Hi all !
>
> I noticed a strange behaviour of the function `class<-` when a class-specific '[[.' method is defined.
>
> Here below a reproducible example :
>
>
> #-------------------------------------------------------------------.
>
> counttt <- 0
>
> `[[.MYCLASS` = function(x, ...) {
> counttt <<- counttt + 1
> # browser()
> x = NextMethod()
> return(x)
> }
>
> df <- as.data.frame(matrix(1:20, nrow=5))
> class(df) <- c("MYCLASS","data.frame")
> counttt
>
> # The same occurs when using structure(, class=) or attr(,"class")<-
> df <- as.data.frame(matrix(1:20, nrow=5))
> df <- structure(df, class=c("MYCLASS","data.frame"))
> attr(df, "class") <- c("MYCLASS","data.frame")
>
> #-------------------------------------------------------------------.
>
> Why in this example `class<-` is calling `[[.MYCLASS` 9 times ?
>
> Is there a way to avoid `class<-` to call `[[.MYCLASS` ?
>
>
> Thank you in advance for your help and suggestions.
This is what I see:
> counttt <- 0
>
> `[[.MYCLASS` = function(x, ...) {
+ counttt <<- counttt + 1
+ # browser()
+ x = NextMethod()
+ return(x)
+ }
>
> df <- as.data.frame(matrix(1:20, nrow=5))
> class(df) <- c("MYCLASS","data.frame")
> counttt
[1] 0
So there's something else going on in your system. Maybe post
sessionInfo()?
Duncan Murdoch