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

[Peng Yu]

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 of using unpublished code.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 .