# R-alpha: R 0.50.a1 problem

Peter Dalgaard BSA p.dalgaard@kubism.ku.dk
28 Jul 1997 21:24:45 +0200

```Kurt Hornik <hornik@ci.tuwien.ac.at> writes:

> R> test2
> function (x)
> {
>         attr(x, "call") <- sys.call()
>         x
> }
> R> test2(x)
> Error: stack overflow
> ********************************************************
>
> Using the attr() form results in an endless loop ...

Sounds familiar. The "assignment causes evaluation effect". Hey,
here's an amusing variant:

> fff<-function(){cll<-substitute(ls());print(cll);x<-1;
attr(x,"junk")<-cll;x}
> fff
function ()
{
cll <- substitute(ls())
print(cll)
x <- 1
attr(x, "junk") <- cll
x
}
> fff()
ls()
[1] 1
attr(,"junk")
[1] "*tmp*" "cll"   "x"
> fff
function ()
{
cll <- substitute(ls())
print(cll)
x <- structure(1, junk = c("*tmp*", "cll", "x"))
attr(x, "junk") <- cll
x
}
>

...I know that R is a functional programming language and that
functions can write and modify other functions, but this seems to be
overdoing it a bit, donchathinkso <evil grin>?

--
O__  ---- Peter Dalgaard             Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics     2200 Cph. N
(*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907
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```