[Rd] Defining a method that behaves like '$'?

Marc Schwartz marc_schwartz at me.com
Fri Jul 9 14:58:51 CEST 2010

You were, in effect, trying to overload the ":" operator, which is of course for defining sequences.

If you are using S4 methods, what is wrong with using the default "@" as the extraction syntax (eg. a at name) to get at slots?

See ?"@" and ?slot


Marc Schwartz

On Jul 9, 2010, at 7:49 AM, Renaud Gaujoux wrote:

> Alright.
> Maybe the symbol I chose was not appropriate. I tried ':' to be able to do 'a:name' with 'a' a S4 object.
> I get the following error:
> Error in genericForPrimitive(f) :
>  methods may not be defined for primitive function ":" in this version of R
> Does there exist any symbol that would be suitable for the job?
> Thanks
> -- 
> Renaud Gaujoux
> Computational Biology - University of Cape Town
> South Africa
> On 09/07/2010 14:29, Duncan Murdoch wrote:
>> On 09/07/2010 8:18 AM, Renaud Gaujoux wrote:
>>> Hi,
>>> is there a way to define a method say '$$' that would behave like '$' and allow calls like 'a$$name'?
>> No, the parser handles a fixed syntax, and that expression is not legal.  You could do it with
>> a %$$% name
>> using the infix operator syntax.  (I think the description in the R Language Definition suggests this is not legal, since $$ is not a valid name, but it does currently work and that's unlikely to change.)
>> Duncan Murdoch

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