[R] Why a list of NULL's are reduced to NULL?

[Steve Lianoglou]

On Dec 11, 2009, at 4:45 PM, Peng Yu wrote:

> On Fri, Dec 11, 2009 at 2:37 PM, Charlie Sharpsteen
> <chuck at sharpsteen.net> wrote:
>> On Fri, Dec 11, 2009 at 10:24 AM, Peng Yu <pengyu.ut at gmail.com> wrote:
>>> 
>>> How do you figure out all the possibilities?
>> 
>> Well, the "Value" section of the third party function's help page should
>> outline the return types it produces.  If it doesn't cover all cases, write
>> a letter to the package maintainer.  If you are using third party functions
>> that are not packaged with help pages, then this sort of uncertainty is part
>> of using unpublished code.
> 
> A document may not document all the corner cases. Even if it is so,
> you can never be sure unless all the possibilities are examined .

No, you can be sure. Just look at the code of the function that is ill behaved.

As Don asked: are you actually experiencing this problem with a library on CRAN?

--
Steve Lianoglou
Graduate Student: Computational Systems Biology
  |  Memorial Sloan-Kettering Cancer Center
  |  Weill Medical College of Cornell University
Contact Info: http://cbio.mskcc.org/~lianos/contact