[Rd] named empty list

Martin Maechler maechler at stat.math.ethz.ch
Fri Jun 4 11:43:38 CEST 2010

>>>>> "HP" == Hervé Pagès <hpages at fhcrc.org>
>>>>>     on Thu, 03 Jun 2010 13:25:10 -0700 writes:

    HP> Hi,
    HP> I just realized that a named empty list is displayed the same
    HP> way as an empty list:

    >> list(aa=2:5)[0]
    HP> list()
    >> list()
    HP> list()

    HP> For empty atomic vectors, the print method makes the difference:

    >> c(aa=3L)[0]
    HP> named integer(0)
    >> integer(0)
    HP> integer(0)

    HP> Maybe lists could do that too?

Yes, I agree.  I have had at least one situation in the past
where I had even been confused for a few minutes by this.
I'm about to add it for R-devel [2.12.0] (only; considering it a
new feature).

Martin Maechler, ETH Zurich

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