R help - Sep 2006 - setMethod

Hello R-help:

I was hoping someone could help me understand a particular function i came
across in a package:

"$.myClass" <- function( x, name ) {
        sym = paste( "foo", name, sep = "_" )
         if( is.loaded(sym) )
             .Call(sym,x)
}

I understand the paste, and .Call part, but I'm not sure how this function
would get called? What exactly is $. ? is it a regular expression? Would a
user call this method directly, or is it an internal function that gets
called according to a class/type.

something similar to:

plot.lm()

Thanks in advance !

Greg

	[[alternative HTML version deleted]]

On 9/22/2006 4:02 PM, Sender wrote:
> Hello R-help:
> 
> I was hoping someone could help me understand a particular function i came
> across in a package:
> 
> "$.myClass" <- function( x, name ) {
>         sym = paste( "foo", name, sep = "_" )
>          if( is.loaded(sym) )
>              .Call(sym,x)
> }
> 
> I understand the paste, and .Call part, but I'm not sure how this
function
> would get called? What exactly is $. ? is it a regular expression? Would a
> user call this method directly, or is it an internal function that gets
> called according to a class/type.
It's the implementation of the "$" function for myClass objects,
so if x
was a myClass object, it would be called when something like

x$name

was used in an expression.  It would call an external function named 
foo_name, passing x as an argument.

Duncan Murdoch
> 
> something similar to:
> 
> plot.lm()
> 
> Thanks in advance !
> 
> Greg
> 
> 	[[alternative HTML version deleted]]
> 
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