[R] obtain names & values of all arguments passed to a function including args passed using the "three dots" ellipsis ( ...) parameter, for use in do.call

[Kelly Thompson]

Sorry for the prior post, I think I found a better way. I can just use
 as.list( match.call()[-1] )

 Here's an example:

fn_return_args_in <- function(x = NULL, y, ...){ return( as.list(
match.call() [-1] ) ) }
do.call(what = fn_return_args_in, args = list(x=1, y=2, zebra = 44,
dog = 'snoopy') )
do.call(what = fn_return_args_in, args = list(y=2, zebra = 44, dog = 'snoopy') )

On Sat, Mar 12, 2022 at 1:29 PM Kelly Thompson <kt1572757 using gmail.com> wrote:
>
> #What are "good" ways to obtain all arguments passed to or being used
> by a function, including arguments passed to the function using the
> "three dots" ellipsis ( ...) parameter, so that these arguments can be
> used in the args parameter of do.call(what, args) .
>
> #I think I've figured out a method that uses environment() and
> match.call() (see example below).
>
> #I'm looking for feedback about problems with my approach, and
> suggestions about better ways to do this.
>
> #Thank you!
>
> #Related posts
> #https://stackoverflow.com/questions/51259346/how-to-get-names-of-dot-dot-dot-arguments-in-r
> #https://stackoverflow.com/questions/35317587/extract-names-of-dataframes-passed-with-dots
> #https://stackoverflow.com/questions/17256834/getting-the-arguments-of-a-parent-function-in-r-with-names
>
> #Example
>
> #Note: "udf_" indicates this is a "user-defined function"
>
> #start udf_return_all_arguments
>     udf_return_all_arguments <- function (...)  {
>
> #obtain all arguments passed to or being used by a function, including
> arguments passed to the function using the "three dots" ellipsis (
> ...) parameter
> #
> #this obtains the arguments for parameters explicitly listed in the function
>         env <- as.list( environment() )
>
> #this obtains the arguments for parameters NOT explicitly listed in
> the function and included    using the 3 dots ellipses ( ... )
> parameters feature
>         mc <- match.call(expand.dots = FALSE)
>         dots <- as.list( mc$...)
>
> #these are all the arguments from the function
>         args_in <-  c(env, dots)
>
>         return(args_in)
>
>     } # end udf_return_all_arguments
>
> ################################################################
>
> #start udf_pass_all_argumens_to_do_call
>     udf_pass_all_argumens_to_do_call <- function(x, y, z = NULL, na.rm
> = T, FUN, ... ) {
>
> #obtain all arguments passed to or being used by a function, including
> arguments passed to the function using the "three dots" ellipsis (
> ...) parameter
> #
> #this obtains the arguments for parameters explicitly listed in the function
>         env <- as.list( environment() )
>
> #this obtains the arguments for parameters NOT explicitly listed in
> the function and included using the 3 dots ellipses ( ... ) parameters
> feature
>         mc <- match.call(expand.dots = FALSE)
>         dots <- as.list( mc$...)
>
> #these are all the arguments from the function
>         args_in <-  c(env, dots)
>
>         do.call( what = FUN, args = args_in)
>
>     } #end udf_pass_all_argumens_to_do_call
>
>     my_list_all_args <- udf_pass_all_argumens_to_do_call(x = 123, y =
> 456, FUN = udf_return_all_arguments, non_specified_paramter = "this is
> an example")
>     my_list_all_args
> ### end of example