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

From: Spencer Graves <>
Date: Sun, 10 Apr 2011 07:18:28 -0700

On 4/10/2011 6:10 AM, Duncan Murdoch wrote:

> 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<>
>>>>> 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.

       I'm sorry:  I did not intend to fool codetools.  ;-)

       I just wanted to provide sensible defaults in a way that seemed 
obvious to me.

       Thanks again for all your work on Rtools and the R project more generally. Spencer

> Duncan Murdoch

Spencer Graves, PE, PhD
President and Chief Operating Officer
Structure Inspection and Monitoring, Inc.
751 Emerson Ct.
San José, CA 95126
ph:  408-655-4567

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