[Rd] Wish there were a "strict mode" for R interpreter. What about You?

[Spencer Graves]

On 4/9/2011 6:12 PM, Duncan Murdoch wrote:
> On 11-04-09 7:02 PM, Spencer Graves wrote:
>> On 4/9/2011 2:31 PM, Hadley Wickham wrote:
>>> On Sat, Apr 9, 2011 at 2:51 PM, Paul Johnson<pauljohn32 at gmail.com>   
>>> wrote:
>>>> Years ago, I did lots of Perl programming. Perl will let you be lazy
>>>> and write functions that refer to undefined variables (like R does),
>>>> but there is also a strict mode so the interpreter will block anything
>>>> when a variable is mentioned that has not been defined. I wish there
>>>> were a strict mode for checking R functions.
>>>>
>>>> Here's why. We have a lot of students writing R functions around here
>>>> and they run into trouble because they use the same name for things
>>>> inside and outside of functions. When they call functions that have
>>>> mistaken or undefined references to names that they use elsewhere,
>>>> then variables that are in the environment are accidentally used. Know
>>>> what I mean?
>>>>
>>>> dat<- whatever
>>>>
>>>> someNewFunction<- function(z, w){
>>>>     #do something with z and w and create a new "dat"
>>>>     # but forget to name it "dat"
>>>>      lm (y, x, data=dat)
>>>>     # lm just used wrong data
>>>> }
>>>>
>>>> I wish R had a strict mode to return an error in that case. Users
>>>> don't realize they are getting nonsense because R finds things to fill
>>>> in for their mistakes.
>>>>
>>>> Is this possible?  Does anybody agree it would be good?
>>>
>>>> library(codetools)
>>>> checkUsage(someNewFunction)
>>> <anonymous>: no visible binding for global variable ‘y’
>>> <anonymous>: no visible binding for global variable ‘x’
>>> <anonymous>: no visible binding for global variable ‘dat’
>>>
>>> Which also picks up another bug in your function ;)
>>
>>         Is this run by "R CMD check"?  I've seen this message.
>>
>>
>>         "R CMD check" will give this message sometimes when I don't feel
>> it's appropriate.  For example, I define a data object ETB in a package,
>> then give that as the default in a function call like
>> f(data.=ETB){if(missing(data.))data(ETB);  data.}.  When I run "R CMD
>> check", I get "no visible binding for global variable 'ETB'", even
>> though the function is tested and works during R CMD check.
>
> What is ETB?  Your code is looking for a global variable by that name, 
> and that's what codetools is telling you.

Duncan:  Thanks for the question.


ETB is a data object in my package.  codetools can't find it because 
data(ETB) is needed before ETB becomes available.  codetools is not 
smart enough to check to see if ETB is a data object in the package.


Spencer

>
> Duncan Murdoch


-- 
Spencer Graves, PE, PhD
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