How do you construct a function from a list?
Duncan Murdoch writes:
I'm trying to get a data.restore function to work on functions. One thing I can't figure out: how do you construct a function from it's component parts?
For example, I can construct a for loop as
forloop <-
as.call(list(as.name('for'),as.name('i'),1,as.call(list(as.name('junk')))))
which results in
for (i in 1) junk()
But how do I put that in a function? For example, I'd like the function
function() for (i in 1) junk()
but as.function(list(forloop)) results in
function () list(for (i in 1) junk())
which returns the for loop in a list, it doesn't execute it. How do I construct the function?
(This might be a bug in as.function, because
as.function(c(alist(a=,b=2),forloop))
returns the expected function
function (a, b = 2) for (i in 1) junk()
It's just that I can't seem to find a way to do it when there are no arguments.)
Duncan,
I think the easiest approach is to do
foo <- function() {}
body(foo) <- forloop
Re the above, I guess Peter would know more about this but is currently
swamped with other work. I also observe that
R> as.function(alist(forloop))
function ()
list(forloop)
R> as.function(list(forloop))
function ()
list(for (i in 1) junk())
which does not seem right.
-k
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