[R] where does the null come from?

[Wacek Kusnierczyk]

Peter Dalgaard wrote:
> Wacek Kusnierczyk wrote:
>   
>>     m = matrix(1:4, 2)
>>
>>     apply(m, 1, cat, '\n')
>>     # 1 2
>>     # 3 4
>>     # NULL
>>
>> why the null?
>>     
>
> It comes from unlist()ing a list of NULLs, which in turn are the return
> values of cat().
>   

yes;  i'd think i'd get a list of nulls, but...


> It is arguably a design-buglet not to return list(NULL, NULL), but the
> internal logic is to unlist() unless the first element is.recursive (and
> NULL is not) or the return values have different length() (and all are
> zero). It _is_, however, in accordance with the documentation (see the
> Value: section):
>   

... i agree the actual outcome is appropriately explained in the docs. 
i don't think it has no merit, but it's a bit surprising at first.

thanks,
vQ