Is an object of a desired type?
is.altrep(x) is.shared(x, recursive = TRUE)
x
an R object
recursive
Logical, whether a data.frame can be treated as a shared object. If TRUE, a data.frame is called a shared object if and only if all of its columns are shared objects.
data.frame
TRUE
A logical value
x = share(1:10) is.altrep(x) is.shared(x)