Thanks Tony (and others), for getting me started. I eventually ended up with:
TopLevel$build_accessor <- function(., extra_args = c()) {
layer <- if (.$class() %in% c("geom","stat", "position")) c(
list(mapping=NULL,data=NULL),
compact(list(
geom = if (exists("default_geom", .)) .$default_geom()$objname,
stat = if (exists("default_stat", .)) .$default_stat()$objname,
position = if (exists("default_pos", .)) .$default_pos()$objname
))
)
params <- .$params()
params <- params[names(params) != "..."]
args <- c(layer, params)
body <- ps(
.$myName(), "$", "new(",
if (length(args) > 0) ps(names(args),"=", names(args), collase =", "),
if (length(extra_args) > 0) ps(names(extra_args),"=", extra_args,
collase =", "),
"...",
")"
)
f <- function() {}
formals(f) <- as.pairlist(c(args, alist(... =)))
body(f) <- parse(text = body)
environment(f) <- globalenv()
f
}
-- obviously there are far more ggplot details in there than I had
first anticipated.
Hadley
On Mon, Feb 25, 2008 at 12:24 AM, Tony Plate <[EMAIL PROTECTED]> wrote:
> Maybe something like this? (though it seems like it might be more
> straightforward to do this sort of thing by text-processing a source
> file then source'ing it in R).
>
> > f <- function(a, b, c) c(a=a,b=b,c=c)
> > attr(f, "source") <- NULL
> > f
> function (a, b, c)
>
> c(a = a, b = b, c = c)
> > g1 <- f
> > ff <- formals(f)
> > argtrans <- c(a="d", b="e", c="f")
> > names(ff) <- argtrans
> > g2 <- as.function(c(ff, as.call(c(list(as.name("f")),
> lapply(argtrans, as.name)))))
> > g2
> function (d, e, f)
> f(a = d, b = e, c = f)
> > f(1,2,3)
> a b c
> 1 2 3
> > g1(a=1,b=2,c=3)
> a b c
> 1 2 3
> > g2(d=1,e=2,f=3)
> a b c
> 1 2 3
> >
>
> -- Tony Plate
>
>
>
>
> hadley wickham wrote:
> > On Sat, Feb 23, 2008 at 5:52 PM, Gabor Grothendieck
> > <[EMAIL PROTECTED]> wrote:
> >
> >> I assume he wants to be able to change the
> >> formals although its confusing since the example
> >> uses the same formals in both cases.
> >>
> >
> > Yes, that was an important point that I forgot to mention! Thanks for
> > the pointer to formals but it doesn't work in this case:
> >
> > function (a = 1, b = 2, c = 3)
> > g(...)
> >
> >> f(c=5)
> >>
> > Error in f(c = 5) : '...' used in an incorrect context
> >
> > Hadley
> >
> >
> >
>
>
--
http://had.co.nz/
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