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

From: Duncan Murdoch <murdoch.duncan_at_gmail.com>
Date: Sun, 10 Apr 2011 09:10:52 -0400

On 11-04-09 9:22 PM, Spencer Graves wrote:

> 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.

Okay, I understand what you are trying to do. Yes, you have fooled codetools in this instance.

Duncan Murdoch



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