R devel - Feb 2008 - how to write dput-able objects

Hi,

One way of doing object-oriented programming in R is to use function environment
to hold object's data, see for example
@Article{Rnews:Chambers+Lang:2001a,
  author       = {John M. Chambers and Duncan Temple Lang},
  title        = {Object-Oriented Programming in {R}},
  journal      = {R News},
  year        = 2001,
  volume       = 1,
  number       = 3,
  pages        = {17--19},
  month        = {September},
  url        = http,
  pdf        = Rnews2001-3
}

One deficiency of this approach is that dput() does not export all data
pertained to the object. For example
> objfactory <- function(nm) {
+   list(name = function() nm)
+ }
>
>
> obj <- objfactory('foo')
>
> obj$name()
[1] "foo"
> dput(obj)
structure(list(name = function ()
nm), .Names = "name")
As one can see the data piece of the obj, nm='foo', is not exported. Is
there a way to modify the original approach so that dput() will produce a
self-sufficient dump of the object?

Thanks,
Vadim

	[[alternative HTML version deleted]]

You might want to look at the proto package.  proto objects won't
immediately dput either but it would not be hard to convert them to
restorable character strings because the proto methods normally
have their object as their parent environment so its implicit in the
definition.  First define a proto object p with one variable 'a' and one
method 'f' and a child object, q, whose 'a' component overrides
the
'a' in its parent.
> library(proto)
> p <- proto(a=1, f = function(.) .$a <- .$a + 1)
> q <- p$proto(a = 2)
> p$as.list()
$a
[1] 1

$f
function(.) .$a <- .$a + 1
<environment: 0x01d6e284>
> name.proto(p)
[1] "p"
> name.proto(p$parent.env())
[1] "R_GlobalEnv"
> q$as.list()
$a
[1] 2
> name.proto(q)
[1] "q"
> name.proto(q$parent.env())
[1] "p"

Note that the strings above have everything
you would need to restore them.  We don't
need the environment since we already know that
f's environment must be p as it belongs to p.

On Mon, Feb 25, 2008 at 12:47 PM, Vadim Organovich
<vogranovich at jumptrading.com> wrote:
> Hi,
>
> One way of doing object-oriented programming in R is to use function
environment to hold object's data, see for example
> @Article{Rnews:Chambers+Lang:2001a,
>  author       = {John M. Chambers and Duncan Temple Lang},
>  title        = {Object-Oriented Programming in {R}},
>  journal      = {R News},
>  year        = 2001,
>  volume       = 1,
>  number       = 3,
>  pages        = {17--19},
>  month        = {September},
>  url        = http,
>  pdf        = Rnews2001-3
> }
>
> One deficiency of this approach is that dput() does not export all data
pertained to the object. For example
>
> > objfactory <- function(nm) {
> +   list(name = function() nm)
> + }
> >
> >
> > obj <- objfactory('foo')
> >
> > obj$name()
> [1] "foo"
> > dput(obj)
> structure(list(name = function ()
> nm), .Names = "name")
> As one can see the data piece of the obj, nm='foo', is not
exported. Is there a way to modify the original approach so that dput() will
produce a self-sufficient dump of the object?
>
> Thanks,
> Vadim
>
>        [[alternative HTML version deleted]]
>
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