[Rd] NROW and NCOL on NULL

[Ben Bolker]

    This is certainly worth discussing, but there's always a heavy 
burden of back-compatibility; how much better would it be for NCOL and 
NROW to both return zero, vs. the amount of old code that would be broken?

   Furthermore, the reason for this behaviour is justified as 
consistency with the behaviour of as.matrix() and cbind() for 
zero-length vectors, from ?NCOL:

      ## as.matrix() produces 1-column matrices from 0-length vectors,
      ## and so does cbind() :

  (of course you could argue that this behaviour should be changed as 
well ...)


On 2023-09-23 3:41 p.m., Simone Giannerini wrote:
> I know it's documented and I know there are other ways to guard
> against this behaviour, once you know about this.
> The point is whether it might be worth it to make NCOL and NROW return
> the same value on NULL and make R more consistent/intuitive and
> possibly less error prone.
> 
> Regards,
> 
> Simone
> 
> On Sat, Sep 23, 2023 at 7:50 PM Duncan Murdoch <murdoch.duncan using gmail.com> wrote:
>>
>> It's been documented for a long time that NCOL(NULL) is 1.  What
>> particular problems did you have in mind?  There might be other ways to
>> guard against them.
>>
>> Duncan Murdoch
>>
>> On 23/09/2023 1:43 p.m., Simone Giannerini wrote:
>>> Dear list,
>>>
>>> I do not know what would be the 'correct' answer to the following but
>>> I think that they should return the same value to avoid potential
>>> problems and hard to debug errors.
>>>
>>> Regards,
>>>
>>> Simone
>>> ---------------------------------------
>>>
>>>> NCOL(NULL)
>>> [1] 1
>>>
>>>> NROW(NULL)
>>> [1] 0
>>>
>>>> sessionInfo()
>>> R version 4.3.1 RC (2023-06-08 r84523 ucrt)
>>> Platform: x86_64-w64-mingw32/x64 (64-bit)
>>> Running under: Windows 11 x64 (build 22621)
>>>
>>> Matrix products: default
>>>
>>>
>>> locale:
>>> [1] LC_COLLATE=Italian_Italy.utf8  LC_CTYPE=Italian_Italy.utf8
>>> [3] LC_MONETARY=Italian_Italy.utf8 LC_NUMERIC=C
>>> [5] LC_TIME=Italian_Italy.utf8
>>>
>>> time zone: Europe/Rome
>>> tzcode source: internal
>>>
>>> attached base packages:
>>> [1] stats     graphics  grDevices utils     datasets  methods   base
>>>
>>> loaded via a namespace (and not attached):
>>> [1] compiler_4.3.1
>>>
>>
> 
>