R devel - Nov 2007 - slots of type "double"

Hi,

Any idea why S4 doesn't allow slots of type "double"?

  > setClass("A", representation(a="double"))
  Error in makePrototypeFromClassDef(properties, ClassDef, immediate, where) : 
    in making the prototype for class "A" elements of the prototype
failed to
match the corresponding slot class: a (class ?double? )

"numeric", "integer", "character",
"complex", "raw", etc... they all work
but "double" doesn't. Any reason for this strange exception?

Thanks!
H.

On Nov 13, 2007, at 3:36 AM, hpages at fhcrc.org wrote:
> Any idea why S4 doesn't allow slots of type "double"?
>
Type (as in storage type and "double" is a storage type) has nothing  
to do with classes. You cannot create slots for types, only for classes.

>> setClass("A", representation(a="double"))
>  Error in makePrototypeFromClassDef(properties, ClassDef, immediate,  
> where) :
>    in making the prototype for class "A" elements of the
prototype
> failed to
> match the corresponding slot class: a (class ?double? )
>
> "numeric", "integer", "character",
"complex", "raw", etc... they all
> work but "double" doesn't. Any reason for this strange
exception?
>
AFAICS there is no way to create an object of the class "double" (save
for 'faking' it by creating an informal S3 object), so such definition  
is useless. And given this fact, even the internal code is unable to  
create it, so it doesn't match the signature. Note:

 > a=new("double")
 > class(a)
[1] "numeric"
 > is(a,"double")
[1] FALSE

I think it comes from the fact that there is an S4 definition for the  
class "double" which is not valid. That is probably a bug and the  
class definition should be removed.

Cheers,
Simon