On 7/2/2009 2:17 PM, Steve Lianoglou wrote:
> Hi,
>
> I was wondering if I could get R to warn me, or give me a rude
> awakening somehow, if I'm accessing a variable that is out of my
> function's scope.
>
> For example, often times I'm creating a function as I'm testing it in
> the REPL, copying and pasting between both.
>
> As a simple example, I might end up with a function like:
>
> f <- function(a, b) {
> a + b.test
> }
>
> Where b.test was defined in my workspace as I'm mucking about in the
> REPL, but "clearly" I should have written:
>
> f <- function(a,b) {
> a + b
> }
>
> I could go on for a while in my session w/o noticing the problem
> (since b.test is in my global env), and unbeknownst to me, my function
> will keep accessing the "b.test" variable when I really want it to
> work on the "b" var that I'm passing in to it.
>
> Is there some setting or someway I can get R to warn me that "b.test"
> is being accessed outside the scope of my function?
Not really, but the codetools package can analyze your functions and
tell you which ones do things like that. For example,
> f <- function(a, b) {
+ a + b.test
+ }
> checkUsage(f)
<anonymous>: no visible binding for global variable ‘b.test’
or
> checkUsageEnv(globalenv())
f: no visible binding for global variable ‘b.test’
This is normally used in the package test code, but you can use it on
individual functions or environments if you want.
Duncan Murdoch
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