R devel - Mar 2009 - E`<`<rrors in recursive default argument references

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.

            -s

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
>   
when i run these examples, the execution seems to get into an endless
loop with no error messages whatsoever.  how much time does it take
before you get the error?  (using r 2.8.0 and also the latest r-devel).

vQ
>   (function(a = a)  (a)    ) ()
>   (function(a = a)  -a     ) ()
>   
btw. ?'-' talks about '-' as a *binary* operator, but the only
example
given there which uses '-' uses it as a *unary* operator.  since
'-'()
complains that '-' takes 1 or 2 arguments, it might be a good idea to
acknowledge it in the man page.
>   (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.
>   
a bug in excel?

vQ

On Mon, Mar 9, 2009 at 5:40 PM, Wacek Kusnierczyk
<Waclaw.Marcin.Kusnierczyk at idi.ntnu.no> wrote:
> Stavros Macrakis wrote:
>> Tested in: R version 2.8.1 (2008-12-22) / Windows
> when i run these examples, the execution seems to get into an endless
> loop with no error messages whatsoever. ?how much time does it take
> before you get the error? ?(using r 2.8.0 and also the latest r-devel).
In 2.8.1/Windows (32 bit), they return immediately, though the
stack-overflow case is about 13x slower.
> system.time(for (i in 1:100) {trySilent((function(a=a)(a))())})
   user  system elapsed
   0.67    0.00    0.67
> system.time(for (i in 1:100) {trySilent((function(a=a)as.POSIXct(a))())})
   user  system elapsed
   0.05    0.00    0.05

Are you running under 64 bits?  How long does a vanilla infinite
recursion take to fail on your machine?  I get:
> system.time(for (i in 1:100) trySilent({fff <- function()fff(); fff()}))
   user  system elapsed
   0.27    0.00    0.26

         -s

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.


-- 
    O__  ---- Peter Dalgaard             ?ster Farimagsgade 5, Entr.B
   c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
  (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907