[R] Private methods

[Austin, Matt]

.class1 is an 'internal' method in the namespace of the package 'methods'.
It can be accessed with the ::: operator.  A good start for documentation
may be Vol 3/1 of R-News.


>methods:::.class1
function (x) 
class(x)[[1]]
<environment: namespace:methods>

--Matt


-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch]On Behalf Of Matthew Walker
Sent: Friday, August 13, 2004 17:19 PM
To: r-help at stat.math.ethz.ch
Subject: [R] Private methods


Hi,

I'm trying to understand R's object oriented abilities.

I have read (in a very recent email to r-help) that R's methods package 
does not support private methods.  However, I also looked at the source 
for the function "is":

 > is
function (object, class2)
{
    cl <- .class1(object)
    if (missing(class2))
        return(extends(cl))
    if (.identC(cl, class2) || .identC(class2, "ANY"))
        return(TRUE)
    ...

The first line of the function, the assignment to cl, seems to call a 
function called ".class1".  I was unable to see the source for ".class1":

 > .class1
Error: Object ".class1" not found

It seems to me that either (a) I don't understand what I'm doing, or (b) 
".class1" is a very private method.  The help system finds nothing about 
".class1". 

Could someone please help me to understand this.  Most helpful of all 
would be pointers on where I could find more information.  (So far I 
have found only two documents on R's object oriented abilities:  "A 
guide to using S4 Objects" and "A draft of the R language definition".)

Thanks,

Matthew

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