R devel - Apr 2008 - How to create a function calling two functions with unknown number of parameters?

... can be used to represent unknown number of parameters passed into a
function. 

For example, I write a function g. g calls another function f1. 

For example f1 could be different random number generation function. 

when f1=rnorm(), it has 3 parameters n, mean and standard deviation.

when f1=rexp(), it has 2 parameters n and rate. 

g can be defined as

g <- function(f1, ...) {
	f1(...)
}

My problem is what about g calls two functions with unknown number of
parameters.

In this case one ... doesn't help. 

If I define g as follows:

g <- function(f1, f2, ...) {
	f1(...)+f2(...)
}

It seems ... is only passed to f1, it can't be passed to f2. 

Can anybody help me? Thanks!

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Le ven. 4 avr. ? 18:03, ZT2008 a ?crit :
>
>
> ... can be used to represent unknown number of parameters passed  
> into a
> function.
>
> For example, I write a function g. g calls another function f1.
>
> For example f1 could be different random number generation function.
>
> when f1=rnorm(), it has 3 parameters n, mean and standard deviation.
>
> when f1=rexp(), it has 2 parameters n and rate.
>
> g can be defined as
>
> g <- function(f1, ...) {
> 	f1(...)
> }
>
> My problem is what about g calls two functions with unknown number of
> parameters.
>
> In this case one ... doesn't help.
>
> If I define g as follows:
>
> g <- function(f1, f2, ...) {
> 	f1(...)+f2(...)
> }
>
> It seems ... is only passed to f1, it can't be passed to f2.
You should get around what you want with something along the lines of

dots <- list(...)
argf <- formals(f)
argg <- formals(g)

and then extracting from 'dots' elements corresponding to 'argf'
and
'argg' (using their names).

HTH
>
>
> Can anybody help me? Thanks!
>
> -- 
> View this message in context:
http://www.nabble.com/How-to-create-a-function-calling-two-functions-with-unknown-number-of-parameters--tp16501233p16501233.html
> Sent from the R devel mailing list archive at Nabble.com.
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
---
   Vincent Goulet, Associate Professor
   ?cole d'actuariat
   Universit? Laval, Qu?bec
   Vincent.Goulet at act.ulaval.ca   http://vgoulet.act.ulaval.ca

ZT2008 wrote:
> 
> ... can be used to represent unknown number of parameters passed into a
> function. 
> 
> For example, I write a function g. g calls another function f1. 
> 
> For example f1 could be different random number generation function. 
> 
> when f1=rnorm(), it has 3 parameters n, mean and standard deviation.
> 
> when f1=rexp(), it has 2 parameters n and rate. 
> 
> g can be defined as
> 
> g <- function(f1, ...) {
> 	f1(...)
> }
> 
> My problem is what about g calls two functions with unknown number of
> parameters.
> 
> In this case one ... doesn't help. 
> 
> If I define g as follows:
> 
> g <- function(f1, f2, ...) {
> 	f1(...)+f2(...)
> }
> 
> It seems ... is only passed to f1, it can't be passed to f2. 

No, it is passed to both:

  g <- function(f1, f2, ...) {
      f1(...) + f2(...)
  }
  f1 <- function(a) print(a)
  f2 <- function(a) print(a)
  g(f1, f2, 5)

[1] 5
[1] 5
[1] 10


> Can anybody help me? Thanks!
Well, what you requested already works...

If you want to pass different arguments to f1 and f2, you might want to 
specify two *lists* of arguments for f1() and f2() in g() and call f1() 
and f2() by do.call() within g().

Uwe Ligges