[R] Help with using 'get' function and variable scope

[Duncan Murdoch]

On 4/18/2008 9:19 AM, Gabor Grothendieck wrote:
> On Fri, Apr 18, 2008 at 7:49 AM, Duncan Murdoch <murdoch at stats.uwo.ca> wrote:
>> On 18/04/2008 7:27 AM, Gabor Grothendieck wrote:
>> > If you define your functions in the loop you can it directly
>> > since then the scoping rules work in your favor:
>> >
>> > for(i in 1:4) {
>> >  f <- function() i*i
>> >  print(f())
>> > }
>> >
>>
>> f doesn't need to be in the loop, it just needs to be defined in the same
>> environment as i was defined in.  Loops in R don't create new local frames.
>>
> 
> That's a good point. Do you know if R will optimize out constant expressions
> from a loop?

It doesn't.  Luke Tierney's experimental byte code compiler might do 
optimizations like that, but the regular evaluator does very little 
inspection of what  it is evaluating.

Duncan Murdoch