Curry: proposed new functional programming, er, function.
On Thu, May 5, 2011 at 9:32 AM, Hadley Wickham <hadley at rice.edu> wrote:
On Thu, May 5, 2011 at 8:25 AM, Hadley Wickham <hadley at rice.edu> wrote:
And it seems to work ok in terms of preserving evaluation (I can't how it could be any different to making the anonymous function yourself, unless I've missed something subtle with environments and scoping)
Which indeed I have. ?Hmmm, need to think about this more.
Ok, next version. ?To follow the usual rules of function scope, we
need to make sure the environment of the function is set to the
environment in which it is created.
? ?Curry <- function(FUN, ...) {
? ? ?args <- match.call(expand.dots = FALSE)$...
? ? ?args$... <- as.name("...")
? ? ?env <- parent.frame()
? ? ?if (is.name(FUN)) {
? ? ? ?fname <- FUN
? ? ?} else if (is.character(FUN)) {
? ? ? ?fname <- as.name(FUN)
? ? ?} else if (is.function(FUN)){
? ? ? ?fname <- as.name("FUN")
? ? ? ?env$FUN <- FUN
? ? ?} else {
? ? ? ?stop("FUN not function or name of function")
? ? ?}
? ? ?curry_call <- as.call(c(list(fname), args))
? ? ?f <- eval(call("function", as.pairlist(alist(... = )), curry_call))
? ? ?environment(f) <- env
? ? ?f
? ?}
But I've probably forgotten something else. ?Hopefully Luke will chime
in if I'm proceeding down a path that can never be made to work
completely correctly.
There is some question of whether it should default to the current environment or the original function's environment. If the curried function were regarded as part of a new object whose environment is the current environment then having the current environment (i.e. the object's environment) makes sense but if its regarded purely as an operation on the original function then the original function's environment makes more sense. In any case, an envir= argument to allow the user to specify it would be desirable. Perhaps it could specify the environment to assign (or if a logical or keyword were specified it would indicate which of the two possibilities just mentioned to use to make the common choices easy to specify).
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