I think there isn't a way to make this work other than calling `is.na<-`
explicitly:
x <- b$`is.na<-`(x, TRUE)
It seems like a reasonable suggestion to make
b$is.na(x) <- TRUE
work as long as b is an environment.
If you wanted it to work when b was a list, it would be more problematic
because of partial name matching. E.g. suppose b was a list containing
functions partial(), partial<-(), and part<-(), and I call
b$part(x) <- 1
what would be called?
Duncan Murdoch
On 27/08/2023 10:59 a.m., Konrad Rudolph wrote:
Hello all,
I am wondering whether it’s at all possible to call a replacement function
in a custom environment. From my experiments this appears not to be the
case, and I am wondering whether that restriction is intentional.
To wit, the following works:
x = 1
base::is.na(x) = TRUE
However, the following fails:
x = 1
b = baseenv()
b$is.na(x) = TRUE
The error message is "invalid function in complex assignment". Grepping the
R code for this error message reveals that this behaviour seems to be
hard-coded in function `applydefine` in src/main/eval.c: the function
explicitly checks for `::` and :::` and permits those assignments, but has
no equivalent treatment for `$`.
Am I overlooking something to make this work? And if not — unless there’s a
concrete reason against it, could it be considered to add support for this
syntax, i.e. for calling a replacement function by `$`-subsetting the
defining environment, as shown above?
Cheers,
Konrad
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