Message-ID: <49B5A475.90105@biostat.ku.dk>
Date: 2009-03-09T23:21:25Z
From: Peter Dalgaard
Subject: E`<`<rrors in recursive default argument references
In-Reply-To: <8b356f880903091213o33e27e8di878e4ec574347015@mail.gmail.com>
Stavros Macrakis wrote:
> Tested in: R version 2.8.1 (2008-12-22) / Windows
>
> Recursive default argument references normally give nice clear errors.
> In the first set of examples, you get the error:
>
> Error in ... :
> promise already under evaluation: recursive default argument
> reference or earlier problems?
>
> (function(a = a) a ) ()
> (function(a = a) c(a) ) ()
> (function(a = a) a[1] ) ()
> (function(a = a) a[[1]] ) ()
> (function(a = a) a$x ) ()
> (function(a = a) mean(a) ) ()
> (function(a = a) sort(a) ) ()
> (function(a = a) as.list(a) ) ()
>
> But in the following examples, R seems not to detect the 'promise
> already under evaluation' condition and instead gets a stack overflow,
> with the error message:
>
> Error: C stack usage is too close to the limit
>
> (function(a = a) (a) ) ()
> (function(a = a) -a ) ()
> (function(a = a) var(a) ) ()
> (function(a = a) sum(a) ) ()
> (function(a = a) is.vector(a) ) ()
> (function(a = a) as.numeric(a) ) ()
>
> I don't understand why the two sets of examples behave differently.
Ouch!!!
This shouldn't happen, I'm pretty sure. In particular not the apparently
unstoppable loop under Linux. Thanks for pointing it out.
--
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