How to bind function arguments

Question

How do I partially bind/apply arguments to a function in R?

This is how far I got, then I realized that this approach doesn't work...

bind <- function(fun,...)
{
  argNames <- names(formals(fun))
  bindedArgs <- list(...)
  bindedNames <- names(bindedArgs)
  function(argNames[!argNames %in% bindedArgs])
   {
   #TODO
  }
}

Thanks!

Answer 1

Here's a version of Curry that both preserves lazy evaluation of function argument, but constructs a function that prints moderately nicely:

Curry <- function(FUN, ...) {
  args <- match.call(expand.dots = FALSE)$...
  args$... <- as.name("...")

  env <- new.env(parent = 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
}

It basically works by generating an anonymous function in exactly the same way you would if you were constructing the partial binding yourself.

Answer 2

Actually, this seems to work as a work around

bind <- function(fun,...)
{
  boundArgs <- list(...)
  formals(fun)[names(boundArgs)] <- boundArgs
  fun
}

However, ideally I want the bound arguments to disappear completely from the new function so that calls to the new function can happen with name specification, e.g. with add <- function(a,b) a+b I would like (bind(add,a=2))(1) to return 3.