Duncan Murdoch wrote:
> On 1/21/2008 9:58 AM, Thomas Petzoldt wrote:
>> Hello Duncan,
>>
>> thank you very much for your prompt reply. When I interpret your answer
>> correctly there seems to be no alternative than either:
>>
>> A) using lots of (possibly private) functions in the package or,
>> B) define dummies for all functions which are in such lists or,
>> C) ignore the NOTE, knowing that it is spurious (BTW: there are several
>> prominent packages on CRAN with unresolved NOTEs).
[...]
> There's another way, which is more R-like, if you really want to avoid
> lots of private functions. That is to create your lists via a function,
> and define the functions in the lists locally within the creator. That
> is, something like this:
>
> MakeListA <- function() {
> foo <- function() {
> 1:10
> }
> bar <-function() {
> log(foo())
> }
> return(list(foo = foo, bar = bar))
> }
>
> fListA <- MakeListA()
>
> This avoids the explicit environment manipulations. Because both foo
> and bar are defined locally within MakeListA, they share an environment
> there, and can see each other (and anything else you chose to define
> locally within MakeListA.)
[...]
Cool! What about the following (AFAIK getting environments is "legal" as
opposed to setting them):
MakeListA <- function() {
foo <- function() {
1:10
}
bar <-function() {
log(foo())
}
return(as.list(environment()))
}
fListA <- MakeListA()
makefun <- function(flist) {
with(flist,
function() bar() + foo()
)
}
toplevel <- makefun(fListA)
toplevel()
## but it is not possible to naively replace functions afterwards:
fListA$bar <- function() cos(foo())
toplevel <- makefun(fListA)
toplevel()
## Error in bar() : could not find function "foo"
Note that it's the same in the "explicit" and in the environment version.
-- Thomas P.
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