Thanks MW! Your comments were very helpful. I also see how the NextMethod() works now.
On Mar 25, 2013, at 5:03 AM, R. Michael Weylandt wrote: > On Mon, Mar 25, 2013 at 6:51 AM, Francisco J. Bido <b...@mac.com> wrote: >> Hi, I'm new to OOP in R so please forgive the naiveness of some of the >> questions. Here are a couple of them. It would be great if you can >> contrast to OOP in Java. > > Java is not the end-all of OOP (in fact S is a good bit older than > Java) and you might find that the Lisp or Dylan object systems are a > better analogy. (I'm only going by hearsay on Dylan; never used it > myself) You might also quickly breeze through: > https://github.com/hadley/devtools/wiki/S3 > >> >> 1. R's S4 appears to centered around a dispatch mechanism which in my >> understanding is just a way to implement polymorphism. Now, here's the snag, >> I thought polymorphism was an aspect of OOP not by itself the definition of >> OOP. What am I missing here? Is any language that implements polymorphism >> automatically OO? >> > > If you accept the immutability of objects, then arguably yes, I > suppose polymorphism gives you a great deal of it. The remaining > weaknesses are generally addressed by the S4 object system. > > (Not immutability of bindings like Haskell, but the fact that x <- y > <- 1:5; y[3] <- 10 won't change x. In theory this is done by creating > a new y with the modified 3rd element and binding the name y to that; > not entirely thus in practice for performance reasons ) > >> 2. Can someone provide a simple example of how NextMethod() works? I read >> some things about but I can't make any sense out of it. >> It's supposed to facilitate inheritance but how? Why is it needed, what >> happens if it's ignored? An example would be useful. Is there a Java >> equivalent of NextMethod()? > > Grepping through R's source, it seems that the print system uses a > fair amount of NextMethod for the AsIs and noquote print methods. You > might take a look at those: also, section 7 of > http://cran.r-project.org/doc/manuals/r-devel/R-exts.html > > MW > > >> >> Many Thanks! >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
