R help - Jan 2011 - ReferenceClasses examples {method}

Dear help, dear John Chambers,
I'm trying to learn OOP-possibilities in R and I was going through the 
documentation 'ReferenceClasses {methods}'. (great work, by the way...)
Reading associated Examples, something bothers me : it seems to me that there 
are errors in 'edit' and 'undo' methods. I think that :
- 'undo' should update 'edits' field with :
length(edits) <<- length(edits) - 1 #(and not - 2)
- and for coherence, 'edit' should store modifications in an
'append'-style :
edits <<- c(edits,list(backup)) #as opposed to c(list(backup),edits)

I hope I'm not wrong.

As a complementary question, suppose one kept 'c(edits,list(backup))',
does
anyone know how todiscard first element(s) of a list? For a vector :
vedits<<-vedits[-1]
But lists can't be selected that way ( edits<<- edits [[-1]] #wrong )

Bye.

Marc


      
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On Jan 28, 2011, at 11:05 AM, Marc Carpentier wrote:
> Dear help, dear John Chambers,
> I'm trying to learn OOP-possibilities in R and I was going through the
> documentation 'ReferenceClasses {methods}'. (great work, by the  
> way...)
> Reading associated Examples, something bothers me : it seems to me  
> that there
> are errors in 'edit' and 'undo' methods. I think that :
> - 'undo' should update 'edits' field with :
> length(edits) <<- length(edits) - 1 #(and not - 2)
> - and for coherence, 'edit' should store modifications in an  
> 'append'-style :
> edits <<- c(edits,list(backup)) #as opposed to c(list(backup),edits)
>
> I hope I'm not wrong.
>
> As a complementary question, suppose one kept  
> 'c(edits,list(backup))', does
> anyone know how todiscard first element(s) of a list? For a vector :
> vedits<<-vedits[-1]
> But lists can't be selected that way ( edits<<- edits [[-1]]
#wrong )
You are confusing "[" and "[["

 > ll <- list(a=1,b=2,cc=3)
 > ll[-1]
$b
[1] 2

$cc
[1] 3
>
-- 

David Winsemius, MD
West Hartford, CT