On 03/10/2012 10:16 AM, Hadley Wickham wrote:
Hi all,
A function has three components: arguments, body and environment. Is
there no base function that allows us to create a function from those
three components?
There is: it is `function`. The parser converts your function
definitions into a call to it. (It has 3 arguments: the formals, the
body, and the srcref. The environment is added when it is evaluated.)
So your make_function below is pretty similar (but because `function` is
primitive, some of the evaluation rules might be different).
Duncan Murdoch
The best I could come up with is:
make_function <- function(args, body, env = parent.frame()) {
args <- as.pairlist(args)
stopifnot(is.language(body))
f <- eval(call("function", args, body))
environment(f) <- env
f
}
mquote <- function(...) as.list(substitute(list(...))[-1])
add <- make_function(mquote(a = 1, b = a), quote(a + b))
add(1)
add(1, 2)
add2 <- make_function(mquote(a = 1, b = a), quote(a + b + d))
d <- 3
add2(1)
Am I missing a built in way to do this? Also, is there a built in
equivalent to my mquote (= multiquote, for producing a named list of
quoted inputs)?
Thanks!
Hadley
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