R devel - Sep 2006 - setMethod("Logic", ...)

Hi


In V&R the "polynomial" class is explicitly specified to have no  
logical operators:

setMethod("Logic", signature(e1="polynomial"),
function(e1,e2){stop
("...")})


  I too have a class of objects for which I want to
specify that Logic operators do not work, but executing



setClass("brob",
          representation = representation 
(x="numeric",positive="logical"),
          prototype      = list(x=numeric(),positive=logical())
          )

setMethod("Logic",signature(e1="brob"), function(e1,e2)
           {
             stop("No logic currently implemented for brob objects")
           }
)


gives me


Error in setMethod("Logic", signature(e1 = "brob"),
function(e1, e2) { :
	no existing definition for function 'Logic'


?Math seems to imply that there is no "Logic" group.

So, what is the correct way to specify that logical operations are
not allowed  for "brob" objects?





--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
  tel  023-8059-7743

Accordng to the S4groupGeneric page, there is no such group.

My guess as to why:

Those operators are not S3 generic in R, and S4 dispatch is piggy-backed 
on S3 dispatch (not necessarily, but for convenience).


On Fri, 1 Sep 2006, Robin Hankin wrote:
> Hi
> 
> 
> In V&R the "polynomial" class is explicitly specified to have
no
> logical operators:
> 
> setMethod("Logic", signature(e1="polynomial"),
function(e1,e2){stop
> ("...")})
> 
> 
>   I too have a class of objects for which I want to
> specify that Logic operators do not work, but executing
> 
> 
> 
> setClass("brob",
>           representation = representation 
> (x="numeric",positive="logical"),
>           prototype      = list(x=numeric(),positive=logical())
>           )
> 
> setMethod("Logic",signature(e1="brob"), function(e1,e2)
>            {
>              stop("No logic currently implemented for brob
objects")
>            }
> )
> 
> 
> gives me
> 
> 
> Error in setMethod("Logic", signature(e1 = "brob"),
function(e1, e2) { :
> 	no existing definition for function 'Logic'
> 
> 
> ?Math seems to imply that there is no "Logic" group.
> 
> So, what is the correct way to specify that logical operations are
> not allowed  for "brob" objects?
> 
> 
> 
> 
> 
> --
> Robin Hankin
> Uncertainty Analyst
> National Oceanography Centre, Southampton
> European Way, Southampton SO14 3ZH, UK
>   tel  023-8059-7743
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
> 
-- 
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