[Rd] Objects in R

[Nathan Whitehouse]

  I think S4 is certainly ok for the "interactivity"
aspect of R.

  And probably avoiding untraceable references and
preserving clarity was important to preserve R's role
as a "playing-with-data" language.  

  But R can be potentially used for much more than it
is, and therein lies the difficulty.  I think a full
and frank discussion about data structures would be
healthy.   Enunciating the design choices for the
current R object model would be a step in the right
direction.

  Cheers,
  Nathan

> One important thing to remember, which I think some
> more 
> experienced programmers may forget, is that R is two
> things---a 
> programming language and an *interactive* system for
> statistics 
> and graphics.  Maintaining the
> "interactive-ableness" of R may 
> have imposed certain design choices.  I personally
> think the 
> current S4 system of generics/methods is quite
> suitable for both 
> the "programming" and "interactive" sides of R.
> 
> Just $0.02.
> 
> -roger
> 
> Nathan Whitehouse wrote:
> > Hi,
> >   A few comments from a fairly experienced R user
> who
> > worked for several years on a R-based
> bioinformatics
> > analysis framework.
> > 
> >   I don't want to misrepresent anyone's views,
> but...
> > 
> >   There are real disadvantages to the
> > "objects-as-C-structs" and functions/methods which
> > "mutate" based on argument type. i.e. S4.
> > 
> >   (1)Novices simply don't understand it.  Students
> are
> > trained in "standard" object-oriented technique
> and
> > this wonkish offshoot(puritanical functional
> > programming) just increases the information costs
> to
> > using R and thus decreases the demand.
> > 
> >   (2)Large frameworks benefit from
> > serializable/storable objects which contain both
> > functionality and modifiable values.  S4 stores
> > "class" information and R.oo does not upon
> > "save()"ing, but there are still real hindrances
> to
> > "trading" objects, which is -extraordinarily-
> > important in creating industrial-variety R-based
> > analysis.
> >   The classical example in my mind is the
> difficulties
> > in implementing a "visitor" pattern in S4.  
> > 
> >   (3)The absence of references means for large
> > datasets and long "analysis flows," there is (1)a
> > hideous amount of memory used storing each
> predecessor
> > analysis or (2)there are awkward "references" that
> > I've seen used like storing the name of the
> reference
> > object in a data slot.
> >   I find the use of environments in R.oo as
> opposed to
> > the glorified LISTSXP of S4 to be a satisfying way
> > around this.
> > 
> >   S4 is a nice step forward.  But R should be open
> to
> > further evolution.  The design choices for S4 and
> the
> > reasons behind abandoning OOP have never been
> > adequately justified in my knowledge.  Instead
> most
> > inquiries have been met by a Sphinx-like silence
> by
> > the core community.
> > 
> >   But the hindrances faced by our friend Ali are
> > common, and even in packages maintained by
> experienced
> > R developers, S4 is implemented shall we say
> curiously
> > as per the specs.
> >   Clearly OOP and R.oo are not the final answer. 
> But
> > some serious discussion about why packages like
> R.oo
> > which "layer" onto the standard functional R are
> > inappropriate is in order.
> > 
> >   It would be great to see R emerge from its niche
> > audience.  I believe that would aid statisticians
> and
> > programmers.  However, a little bit more
> transparency
> > and something beyond a categorical "we just don't
> like
> > that way of doing things" would go a long way
> towards
> > growing the base community of R.
> >  
> >   Cheers,
> >   Nathan Whitehouse
> >   Formerly of Baylor College of Medicine.
> > 
> > Ali, maybe we R-core members are not decent
> enough.
> > But we strongly believe that we don't want to
> advocate
> > yet
> > another object system additionally to the S3 and
> S4
> > one,
> > and several of us have given talks and classes,
> even
> > written
> > books on how to do "decent" object oriented
> > programming 
> > `just' with the S3 and/or S4 object system.
> > 
> > No need of additional "oo" in our eyes.
> > Your main problem is that you assume what "oo"
> means
> > {which may
> > well be true} but *additionally* you also assume
> that
> > OO has to
> > be done in the same way you know it from Python,
> C++,
> > or Java..
> > 
> > Since you are new, please try to learn the S4 way,
> > where methods belong to (generic) functions more
> than
> > to classes in some way, particularly if you
> compare
> > with other
> > OO systems where methods belong entirely to
> classes.
> > This is NOT true for R (and S-plus) and we don't
> want
> > this to
> > change {and yes, we do know about C++, Python,
> > Java,... and
> > their way to do OO}.
> > 
> > Please also read in more details the good advice
> given
> > by Tony
> > Plate and Sean Davis.
> > 
> > Martin Maechler,
> > ETH Zurich
> > 
> > 
> > 
> > Nathan Whitehouse
> > nlwhitehouse at yahoo.com
> > 
> > ______________________________________________
> > R-devel at stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
> > 
> 
> -- 
> Roger D. Peng
> http://www.biostat.jhsph.edu/~rpeng/
> 

Nathan Whitehouse
nlwhitehouse at yahoo.com