From ripley at stats.ox.ac.uk  Fri Sep  1 17:45:45 2006
From: ripley at stats.ox.ac.uk (Prof Brian Ripley)
Date: Fri, 1 Sep 2006 16:45:45 +0100 (BST)
Subject: [Rd] setMethod("Logic", ...)
In-Reply-To: <91AD8AFC-E5A3-4F79-821D-CACC2705333D@soc.soton.ac.uk>
References: <91AD8AFC-E5A3-4F79-821D-CACC2705333D@soc.soton.ac.uk>
Message-ID: <Pine.LNX.4.64.0609011642240.16133@gannet.stats.ox.ac.uk>

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




[Rd] setMethod("Logic", ...)
Prof Brian Ripley