R help - Mar 2006 - Recall for parent

What's the best way to simulate Recall for parent function?
Consider this one-time recursive code:

alwaysEven <- function(x) {
    handleOdd <- function(x) {
        alwaysEven(x-1)    # use Recall-like here
    }

    return(if (x %% 2) handleOdd(x) else x)
}
any2even <- alwaysEven
rm(alwaysEven)
any2even(3)

----------------------------------------------------------
SIGSIG -- signature too long (core dumped)

Here are two ways:


# method 1. nest an extra alwaysEven
alwaysEven <- function(x) {
 alwaysEven <- function(x) {
   handleOdd <- function(x) {
       alwaysEven(x-1)    # use Recall-like here
   }

   return(if (x %% 2) handleOdd(x) else x)
 }
 alwaysEven(x)
}
any2even <- alwaysEven
rm(alwaysEven)
any2even(3)


# method 2.  sys.function

alwaysEven <- function(x) {
   handleOdd <- function(x) {
       sys.function(1)(x-1)    # use Recall-like here
   }

   return(if (x %% 2) handleOdd(x) else x)
}
any2even <- alwaysEven
rm(alwaysEven)
any2even(3)



On 3/29/06, Paul Roebuck <roebuck at mdanderson.org>
wrote:
> What's the best way to simulate Recall for parent function?
> Consider this one-time recursive code:
>
> alwaysEven <- function(x) {
>    handleOdd <- function(x) {
>        alwaysEven(x-1)    # use Recall-like here
>    }
>
>    return(if (x %% 2) handleOdd(x) else x)
> }
> any2even <- alwaysEven
> rm(alwaysEven)
> any2even(3)
>
> ----------------------------------------------------------
> SIGSIG -- signature too long (core dumped)
>
> ______________________________________________
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>

On Wed, 29 Mar 2006, Paul Roebuck wrote:
> What's the best way to simulate Recall for parent function?
> Consider this one-time recursive code:
>
> alwaysEven <- function(x) {
>    handleOdd <- function(x) {
>        alwaysEven(x-1)    # use Recall-like here
>    }
>
>    return(if (x %% 2) handleOdd(x) else x)
> }
> any2even <- alwaysEven
> rm(alwaysEven)
> any2even(3)
You can make anonymous recursive functions with local()

whatever <- local({
               alwaysEven <- function(x) {
                  handleOdd <- function(x) {
                     alwaysEven(x-1)
               }
               return(if (x %% 2) handleOdd(x) else x)
               }
           alwaysEven
           })


 	-thomas

Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle