Using names in function with ellipsis (non standard evaluation?)

I also am not sure exactly what the OP wants and even less sure of what he
needs...

But a possible answer is that a canonical way to do this is just to pass
down the ... list in the definition and specifying a named list of arguments
in the call (as has already been mentioned).

e.g. consider:

g <- function(f,...)f(...)

## so g can accept arbitrary functions with arbitrary arguments

fru <- function(x,y=3)x+y

g(fru,x=2) ## default y used

[1] 5

g(fru,x=2,y=7) ## y argument given explicitly

[1] 9


Please pardon the noise if this is irrelevant.

Cheers,
Bert

On Thu, May 28, 2015 at 12:17 PM, Duncan Murdoch <murdoch.duncan at gmail.com>
wrote:

On 28/05/2015 1:40 PM, Luca Cerone wrote:

Hi everybody,

this is probably a silly question, but I can't find a way to recognize
the names that are passed
to variables in ellipsis.

For example, say I have a "core" function that receives some extra
parameters through ...
e.g.

f <- function(...) {
   params <- c(...)
   #dothehardworkhere using "names(params)"
}

and then I want to create a function g where some of the parameters
are set like:

g <- function(x,y) f(x,y)

I figure I probably have to use to substitute in f, but it is not
clear to me how.

Definitely what I need to achieve is that when I call:

g(1,2) then in f params is the vector c(x=1,y=2);
similarly I want to be able to call g(y=2, x=1)
and have params = c(x=1,y=2) in f.

Can you please help me understanding how to do this?

Sorry, I misunderstood your question.  I didn't notice that g calls f.
You should write g to call f with names on the parameters, i.e.

g <- function(x,y) f(x=x, y=y)

then f will receive the parameters with names on them.  I'd still advise
against using c(...), but it will give you the output you want with that
input; the problem is if your users do something like
g(1:2, 3:4) (which would give c(x1=1, x2=2, y1=3, y2=4)).

Duncan Murdoch