2008/3/7 Ben Bolker <[EMAIL PROTECTED]>:
>
> Despite the spirited arguments of various R-core folks
> who feel that mle() doesn't need a "data" argument, and
> that users would be better off learning to deal with function
> closures, I am *still* trying to make such things work
> in a reasonably smooth fashion ...
>
> Is there a standard idiom for "merging" environments?
> i.e., suppose a function has an environment that I want
> to preserve, but _add_ the contents of a data list --
> would something like this do it? Is there a less ugly
> way?
>
> x <- 0
> y <- 1
> z <- 2
>
> f <- function() {
> x+y+z
> }
>
> f2 <- function(fun,data) {
> L <- ls(pos=environment(fun))
> mapply(assign,names(data),data,
> MoreArgs=list(envir=environment(fun)))
> print(ls(pos=environment(fun)))
> }
>
> f2(f,list(a=1))
I think you're doomed to be ugly if you don't use closures - I think
any explicit manipulation of environments is worse than the implicit
manipulation by closures.
f <- function(data) with(data, x + y + z)
f2 <- function(fun, data) function() fun(data)
f2(f, list(x = 10))()
Although it would be even nicer if you could do:
f <- function() x + y + z
f2 <- function(fun, data) function() with(data, fun())
but I think that's confusing different types of scoping.
Hadley
--
http://had.co.nz/
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