[Rd] S4 'object is not subsettable' in prototype

[Martin Maechler]

>>>>> "Seth" == Seth Falcon <sfalcon at fhcrc.org>
>>>>>     on Fri, 18 Aug 2006 09:54:54 -0700 writes:

    Seth> Martin Maechler <maechler at stat.math.ethz.ch> writes:
    >> I agree you've found an "infelicity" in the current setup,
    >> since
    >> 
    >> > setClass("A", representation(x="numeric"))
    >> [1] "A"
    >> > getClass("A")@prototype
    >> <S4 Type Object>
    >> attr(,"x")
    >> numeric(0)
    >> > length(getClass("A")@prototype)
    >> [1] 1
    >> > getClass("A")@prototype[1]
    >> Error in getClass("A")@prototype[1] : object is not subsettable
    >> > 
    >> 
    >> It's not clear yet to me *what* should be changed.
    >> For my taste, if length(object) returns 1, 
    >> I'd typically want that object[1] should be valid;
    >> but I think we already have some (peculiar) exceptions to that
    >> rule. 

    Seth> I disagree with the notion that length and "[" should be tightly
    Seth> coupled.  An object having length doesn't have to mean that subsetting
    Seth> makes any sense.  For example, an environment has length, but what
    Seth> should env1[1] return?  And with S4 classes, there are many such
    Seth> examples where "[i]" won't make sense.

You are right.  I was rather thinking of  "basic"  objects
rather than highly structured objects such as S4 classes.

Note that for me, an environment belongs into the
category of "peculiar" exceptions ;-)

Martin

    Seth> + seth