[R] "recursive default argument" error

From: <tolga.i.uzuner_at_jpmorgan.com>
Date: Tue, 25 Nov 2008 09:26:58 +0000


Dear R Users,

I have a function foo in a script with default values for some of the parameters as follows:

testparams=list(a=1,b=2,c=3)
foo<-function(x,y,testparams=testparams)

        x+y+testparams$a+testparams$b+testparams$c

When I try to run foo(1,2), I get the following error:

> testparams=list(a=1,b=2,c=3)
> foo<-function(x,y,testparams=testparams)
+ x+y+testparams$a+testparams$b+testparams$c
> foo(1,2)
Error in foo(1, 2) :
  promise already under evaluation: recursive default argument reference or earlier problems?
>

I can obviously rename testparams but I would still like to understand why this breaks. I would have thought the right hand side of "testparams=testparams" would have been evaluated in the namespace outside the script and not the function. How can I force it to be evaluated in the namespace outside the function ?

Thanks in advance,
Tolga

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