[Rd] dubious behaviour of match.arg() with nested functions.

[Hadley Wickham]

This is one of the perils of non-standard evaluation - functions are
no longer referentially transparent.

Hadley

On Mon, Aug 25, 2014 at 9:27 AM, Joris Meys <jorismeys at gmail.com> wrote:
> Dear all,
>
> I initially ran into this problem while rebuilding a package dependent on
> nleqslv. I got the following error:
>
> Error in match.arg(global) : 'arg' must be of length 1
>
> This didn't occur in previous versions of nleqslv, but did in the current
> one (2.4). I think I pinned the problem down to the following example:
>
> Take two functions:
>
> test <- function(x=c("q","r","s"),global=c("d","e","r","z","q")){
>   x <- match.arg(x)
>   global <- match.arg(global)
>   return(list(x,global))
> }
>
> test2 <- function(x=c("q","r","s"),global=c("d","z","q")){
>   test(x=x,global=global)
> }
>
> test2() calls an "internal" function test() that uses the same arguments.
> Note that for x both functions have exactly the same defaults, but not for
> global.
>
> Calling test2() gives the reported error:
>
>> test2()
>  Error in match.arg(global) : 'arg' must be of length 1
>
> I see the point of this error (global is not seen by test2() as default
> settings but as a character vector I presume), but I wonder why this isn't
> the case for x. Is this by design? If so, is there a part of the manual I
> overlooked?
>
> Cheers
> Joris
>
> --
> Joris Meys
> Statistical consultant
>
> Ghent University
> Faculty of Bioscience Engineering
> Department of Mathematical Modelling, Statistics and Bio-Informatics
>
> tel : +32 9 264 59 87
> Joris.Meys at Ugent.be
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