[Rd] Qs: The list of arguments, wrapping functions...

Gabor Grothendieck ggrothendieck at gmail.com
Wed May 20 01:14:00 CEST 2009

match.call() will return the call.   merge.zoo in the zoo package
uses it if you need an example.  as.list(match.call()) will return
a list.

list(...) will return the ... arguments as a list.

$.proto in the proto package allows one to write p$f where p
is a proto object and f is a function and p$f is the function
f(p, ...), i.e. it provides a currying operation.

The Defaults package allows one to dynamically change the
default arguments of functions.

On Tue, May 19, 2009 at 4:22 PM, Kynn Jones <kynnjo at gmail.com> wrote:
> Hi.  I'm pretty new to R, but I've been programming in other languages for
> some time.  I have a couple of questions regarding programming with function
> objects.
> 1. Is there a way for a function to refer generically to all its actual
> arguments as a list?  I'm thinking of something like the @_ array in Perl or
> the arguments variable in JavaScript.  (By "actual" I mean the ones that
> were actually passed, as opposed to its formal arguments, as returned by
> formals()).
> 2. I have a package in which most of the functions have the form:
> the.function <- function(some, list, of, params) {
>    return( some.other.function(the.list.of.params.to.this.function));
> }
> Is there a way that I can use a loop to define all these functions?
> In general, I'm looking for all the information I can find on the subject of
> dynamic function definition (i.e. using code to automate the definition of
> functions at runtime).  I'm most interested in introspection facilities and
> dynamic code generation.  E.g. is it possible to write a module that
> "redefines itself" when sourced?  Or can a function redefine itself when
> first run?  Or how can a function find out about how it was called?
> FWIW, Some of the things I'd like to do are in the spirit of a decorator in
> Python, which is a function that take a function f an argument and return
> another function g that is somehow based on f.  For example, this makes it
> very easy to write functions as wrappers to other simpler functions.
> TIA!
> KJ
>        [[alternative HTML version deleted]]
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