[R] S4 object slot of type 'call'
Prof Brian Ripley
ripley at stats.ox.ac.uk
Mon May 28 19:20:05 CEST 2007
On Mon, 28 May 2007, Uwe Ligges wrote:
> Roberto Brunelli wrote:
>> I'm using an S4 object with a slot of type 'call': I would like to be able to initialize
>> it with something like NULL or NA (indicating that there is no information in the slot)
>> but the value should comply with the fact that it must be of type call.
>> Is there any simple way to obtain this?
> This looks fine:
> > setClass("testCall", representation = representation(call = "call"))
>  "testCall"
> > test <- new("testCall")
> > test
> An object of class "testCall"
> Slot "call":
> Although, I found a bug while playing around:
> cl <- call("round", 10.5)
> cl <- NULL
> ## CRASH using R-2.5.0 on Windows XP
Yes, well, what did you think that would do?
A call is a pairlist (a LANGSXP).  on a pairlist converts it to a
vector list, subsets, and for a LANGSXP converts back. So you have
a 0-length call, and lots of code assumes that a LANGSXP has length at
least one, including deparse (used in printing).
cl <- call("round")
cl <- list(NULL)
might be what you were trying to get.
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
More information about the R-help