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

[Spencer Graves]

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.


       Spencer

> Hadley
>


-- 
Spencer Graves, PE, PhD
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