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

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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Herv? Pag?s

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