[Rd] Functions that write functions in R packages

[hadley wickham]

I'm trying to make wrappers to proto functions (eg. GeomPoint$new())
so that user don't notice that they're using a proto function (ie. use
geom_point()) instead.  I'm hoping I can wrap proto up sufficiently
that only developers need to worry that ggplot uses a completely
different oo system.

Hadley

On 2/23/07, Gabor Grothendieck <ggrothendieck at gmail.com> wrote:
> Not sure what the setup is here but if the objects are
> intended to be proto objects then the accessor functions
> could be placed in the object itself (or in an ancestor object)
> rather than in the global environment.  For example, this inserts
> a function get.v(.) into proto object p for each variable v in p.
>
> library(proto)
>
> make.accessors <- function(p, ...) {
>    lapply(ls(p, ...), f. <- function(v) {
>         nm <- paste("get", v, sep = ".")
>         p[[nm]] <- function(.) {}
>         body(p[[nm]]) <- substitute(.$v, list(v = v))
>         environment(p[[nm]]) <- p
>    })
>    invisible(p)
> }
> make.accessors(p)
> p$get.x()
> p$get.y()
>
> # or the constructor of objects like p could build it right it
> # at object construction time
> make.p <- function(...) make.accessors(proto(...))
> q <- make.p(x = 1, y = 2)
> q$get.x()
> q$get.y()
>
>
> On 2/23/07, hadley wickham <h.wickham at gmail.com> wrote:
> > Dear all,
> >
> > Another question related to my ggplot package:  I have made some
> > substantial changes to the backend of my package so that plot objects
> > can now describe themselves much better.  A consequence of this is
> > that a number of convenience functions that previously I wrote by
> > hand, can now be written automatically.  What is the best practice for
> > creating these functions for bundling in a package?  I see three
> > possible solutions:
> >
> >  * dump function specifications out to a .r file
> >  * dynamically create at package build time so they are including in
> > the package rdata file
> >  * dynamically create at package load time
> >
> > Can anyone offer any advice as to which is preferable? (or if there's
> > a better way I haven't thought of)
> >
> > My code currently looks like this (experimenting with two ways of
> > creating the functions)
> >
> > create_accessors <- function(objects, name, short=NULL) {
> >        lapply(objects, function(x) {
> >                assign(paste(name, x$objname, sep="_"), x$new, pos=globalenv())
> >                if (!is.null(short)) {
> >                        eval(
> >                                substitute(
> >                                        f <- function(plot, ...) plot + add(...),
> >                                        list(
> >                                                add = as.name(paste(name, x$objname, sep="_")),
> >                                                f = as.name(paste(short, x$objname, sep=""))
> >                                        )
> >                                ), envir = globalenv()
> >                        )
> >
> >                }
> >        })
> > }
> >
> > Thanks,
> >
> > Hadley
> >
> > ______________________________________________
> > R-devel at r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
>