Object orientation?

-----Message d'origine-----
De : pd at blueberry.kubism.ku.dk [mailto:pd at blueberry.kubism.ku.dk]De la
part de Peter Dalgaard BSA
Envoye : Wednesday, January 24, 2001 10:39 AM
A : Yves Gauvreau
Cc : R-help at lists. R-project. org
Objet : Re: [R] Object orientation?


"Yves Gauvreau" <cyg at sympatico.ca> writes:

Up to now there is no real problem as I could use the following

construct

for these let and set methods or functions: MyO <-
MyO.let(PropertyName="ThisProperty", ThisValue).

But what I would like to be able to do in order to let or set

(as above) one

of MyO properties for example is only use:
MyO.let(PropertyName="ThisProperty", ThisValue).

So my question is: Can this be done in a proper and acceptable

R fashion?

I know I could use super assign (<<-) but I think some say it's best
avoided.

Generally, that's when people try to turn R (or S) into a macro
language. There could be situations where it's the right thing...

Could you be so kind as to explain what you mean by "turn R (or S) into a
macro language"

However, for this situation, how about something like

class(MyO) <- "foo"
"$<-.foo" <- function(x, name, value)
{
   if ( !is.null(x$let) )
	x$let(PropertyName=name, value)
   else
	x[[name]] <- value
}

MyO$ThisProperty <- ThisValue

(but wouldn't x$let or MyO.let need to have some way of figuring out
which object is its owner??)

Maybe the way I expressed the idea wasn't clear enough or the way I
expressed it wasn't, so I'll try again. I have a personal project where I
would like to use R for it's statistical and graphical capabilities as is
usually the case presumably.

The strategy I thought up would probably be better handled (or easier to
implement) with an object orientation kind of approach. I was able to
identify many objects, in the since of OOP terminology, which would also
need to be handle as a group or as a collection (or as some kind of a
list|data.frame in R terms). I would also require a few of these groups to
be imbedded in higher level object and so on. My first idea was to imbed R
in a program written in a language like C++ for example. Before I start
working in this manner, I thought of investigating the possibilities of
doing all of this in R instead. So I bought "S Programming" from Venables &
Ripley and read it along with other material. So in the process I kind of
ask myself the same thing as you ask me above and I've got no answer. Maybe
I should of ask what are the facilities in R to write or implement an
hierarchy of object (classes) working together as in C++ or as close as
possible to that?

Thanks

Yves

PS I take this occasion to thank all other who tried to help as well.

--
   O__  ---- Peter Dalgaard             Blegdamsvej 3
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907

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