Why does evaluating an expression in system.time() make variables available in global environment?

Question

Can somebody please explain what happens when an expression is evaluated in system.time? In particular, why are any variables that are declared in the ex

Answer 1

I think the expr is evaluated before handling that to the function. POC example:

> st <- function(expr){
+   eval(parse(text=expr))
+ }
> 
> st('aa <- 1')
> aa
Error: object 'aa' not found

So I think the function gets expr as only aa. Another example:

> st <- function(expr){
+   str(expr)
+ }
> 
> st(aa <- 1)
 num 1

I might be wrong, it is rather an intuition :) But thanks, that is a good puzzle!

---

Update:

> system.time(a <- 1)
   user  system elapsed 
      0       0       0 
> a
[1] 1
> rm(a)
> fn <- function() a <- 1
> system.time(fn())
   user  system elapsed 
      0       0       0 
> a
Error: object 'a' not found