R devel - May 2010 - Restrict access to variables in parent environment

Hello All,

By default, a reference of a variable in a function cause R to look
for the variable in the parent environment if it is not available in
the current environment (without generating any errors or warnings).
I'm wondering if there is a way to revert this behaviors, such that it
will not look for the parent environment and will generate an error if
the variable is not available in the current environment. Is this
tuning has to be done at the C level?

-- 
Tom

> Hello All,
>
> By default, a reference of a variable in a function cause R to look
> for the variable in the parent environment if it is not available in
> the current environment (without generating any errors or warnings).
> I'm wondering if there is a way to revert this behaviors, such that it
> will not look for the parent environment and will generate an error if
> the variable is not available in the current environment. Is this
> tuning has to be done at the C level?
Try this:
b <- 1
f <- function(a) {
  b
}

environment(f) <- baseenv()
f()

Hadley

-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/

On 14/05/2010 10:14 AM, thmsfuller066 at gmail.com
wrote:
> Hello All,
>
> By default, a reference of a variable in a function cause R to look
> for the variable in the parent environment if it is not available in
> the current environment (without generating any errors or warnings).
> I'm wondering if there is a way to revert this behaviors, such that it
> will not look for the parent environment and will generate an error if
> the variable is not available in the current environment. Is this
> tuning has to be done at the C level?
You could do that by setting the environment of the function to 
emptyenv(), but it will not be pretty.  Remember that everything in R is 
an object, so you won't have access to the base level objects like +, or 
mean, or any other function.

Duncan Murdoch