[Bioc-devel] Adding a lengths() method to List class

[Michael Lawrence]

It wasn't a conscious choice, but it would slow things down a bit. Not by
much though, since we're already attempting dispatch on length(). I can
make the change.

On Wed, Sep 30, 2015 at 1:33 PM, Hervé Pagès <hpages at fredhutch.org> wrote:

> Hi Michael,
>
> I was expecting this to just work:
>
>   base::lengths(IntegerList(1:4, 1:6))
>
> but it doesn't:
>
>   Error in base::lengths(IntegerList(1:4, 1:6)) :
>     'x' must be a list or atomic vector
>
> The man page says:
>
>      This function loops over ‘x’ and returns a compatible vector
>      containing the length of each element in ‘x’.  Effectively,
>      ‘length(x[[i]])’ is called for all ‘i’, so any methods on ‘length’
>      are considered.
>
> If length(x[[i]]) is called for all i then it should work on any object
> for which [[ is defined. Note that this is what happens with
> base::sapply(), base::mapply(), etc... they all use [[ internally.
>
> Do you know of any reason why lengths() doesn't do this?
>
> Thanks,
> H.
>
>
> On 09/28/2015 09:51 PM, Michael Lawrence wrote:
>
>> That is the plan. Note that we already have elementLengths() that serves
>> the same purpose. It was the direct inspiration for lengths().
>>
>> On Mon, Sep 28, 2015 at 9:41 PM, Peter Hickey <peter.hickey at gmail.com>
>> wrote:
>>
>> The lengths() function was added in R 3.2 to "get the length of each
>>> element of a list or atomic vector (is.atomic) as an integer or numeric
>>> vector." It seems useful to me to have also a similar method defined for
>>> the S4Vectors::List class (and subclasses). What do others think?
>>>
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>>
> --
> Hervé Pagès
>
> Program in Computational Biology
> Division of Public Health Sciences
> Fred Hutchinson Cancer Research Center
> 1100 Fairview Ave. N, M1-B514
> P.O. Box 19024
> Seattle, WA 98109-1024
>
> E-mail: hpages at fredhutch.org
> Phone:  (206) 667-5791
> Fax:    (206) 667-1319
>

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