Re: [R] Defining binary indexing operators

From: Gabor Grothendieck <ggrothendieck_at_gmail.com>
Date: Thu 28 Apr 2005 - 13:13:52 EST

On 4/27/05, Ali - <saveez@hotmail.com> wrote:
>
>
> > > >
> > > > Here is an example. Note that $ does not evaluate y so you have
> > > >to do it yourself:
> > > >
> > > >x <- structure(3, class = "myclass")
> > > >y <- 5
> > > >foo <- function(x,y) x+y
> > > >"$.myclass" <- function(x, i) { i <- eval.parent(parse(text=i));
> foo(x,
> > > i)
> > > >}
> > > >x$y # structure(8, class = "myclass")
> > >
>
> If I got it right, in the above example you provided '$' is defined as a
> method for a S3 class. How is it possible to do the same with a S4 class.
> If
> this is not possible, what is the best way to define the '$' operator
> whose
> first arguments is a S4 object and doesn't overwrite the global
> definition?
>
> The myclass example is defined as an S3 method. In the above its defined
> as a function, not a method.

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