[Rd] anonymous function parsing bug?
William Dunlap
wdunlap at tibco.com
Fri Oct 21 17:00:28 CEST 2016
Here is a simplified version of your problem
> { sqrt }(c(2,4,8))
[1] 1.414214 2.000000 2.828427
Do you want that to act differently?
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Fri, Oct 21, 2016 at 6:10 AM, Wilm Schumacher <wilm.schumacher at gmail.com>
wrote:
> Hi,
>
> I hope this is the correct list for my question. I found a wired behaviour
> of my R installation on the evaluation of anonymous functions.
>
> minimal working example
>
> ###
> f<-function(x) {
> print( 2*x )
> }(2)
>
> class(f)
>
> f(3)
>
> f<-function(x) {
> print( 2*x )
> }(4)(5)
>
> f(6)
> ###
>
> leads to
>
> ###
> > f<-function(x) {
> + print( 2*x )
> + }(2)
> >
> > class(f)
> [1] "function"
> >
> > f(3)
> [1] 6
> Error in f(3) : attempt to apply non-function
> >
> > f<-function(x) {
> + print( 2*x )
> + }(4)(5)
> >
> > f(6)
> [1] 12
> Error in f(6) : attempt to apply non-function
>
> ###
>
> is this a bug or desired behavior? Using parenthesis of coures solves the
> problem. However, I think the operator precedence could be the problem
> here. I looked at the "./src/main/gram.y" and I think that the line 385
> | FUNCTION '(' formlist ')' cr expr_or_assign %prec LOW
> should be of way higher precedence. But I cannot forsee the side effects
> of that (which could be horrible in that case).
>
> If this is the desired behaviour and not a bug, I'm very interested in the
> rational behind that.
>
> Best wishes,
>
> Wilm
>
> ps:
>
> $ R --version
> R version 3.3.1 (2016-06-21) -- "Bug in Your Hair"
>
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