[Rd] access an element with empty name

[Serguei Sokol]

Le 14/05/2018 à 15:55, Kurt Hornik a écrit :
>>>>>> Serguei Sokol writes:
>> Hi,
>> I came across a case where I cannot access a list element by its empty name.
>> Minimal example can be constructed as
>>       x=list("A", 1)
>>       names(x)=c("a", "")
>>       x[["a"]]
>>       #[1]  "A"
>>       x[[""]]
>>       #NULL
>>       x$`a`
>>       #[1]  "A"
>>       x$``
>>       # Error: attempt to use zero-length variable name
>>       # but we can still access the second element by its index
>>       x[[2]]
>>       #[1] 1
>> To my mind, it should be perfectly legal to access an element by an
>> empty name as we can have for example
>>       match("", names(x))
>>       #[1] 2
>> Hence a traditional question: is it a bug or feature?
> A feature according to the docs: ? Extract says
>
>      Neither empty (‘""’) nor ‘NA’ indices match any names, not even
>      empty nor missing names.
>

Thanks Kurt, I missed that one.