Environments in R, mapply and get

Question

Let x<-2 in the global env:

x <-2 
x
[1] 2

Let a be a function that defines another x locally and

Answer 1

The issue is an interplay with built-in C code. Namely, considering the following:

fx <- function(x) environment()
env <- NULL; fn <- function() { env <<- environment(); mapply(fx, 1)[[1]] }

Then

env2 <- fn()
identical(env2, env)
# [1] FALSE
identical(parent.env(env2), env)
# [1] FALSE
identical(parent.env(env2), globalenv())
# [1] TRUE

More specifically, the problem lies in the underlying C code, which fails to consider executing environment, and hands it off to an as-is underlying C eval call which creates a temp environment branching directly off of R_GlobalEnv.

Note this really is what is going on, since no level of stack nesting fixes the issue:

env <- NULL; fn2 <- function() { env <<- environment(); (function() { mapply(fx, 1)[[1]] })() }
identical(parent.env(fn2()), globalenv())
# [1] TRUE