[Rd] Parser bug? A comma too much.

[peter dalgaard]

As a general matter, empty arguments are allowed and are used meaningfully in some contexts, notably A[i,], which is syntactic sugarcoating of "["(A,i,).

I.e., these are different:

> "["(Sigma,2,) # 2nd row
[1] 0.077 0.168
> "["(Sigma,2) # 2nd element
[1] 0.077


It is somewhat rare to have an empty last argument, intermediate ones are more common:

> seq(0,1,,5)
[1] 0.00 0.25 0.50 0.75 1.00

-pd


> On 16 Sep 2022, at 16:33 , Rui Barradas <ruipbarradas using sapo.pt> wrote:
> 
> Hello,
> 
> Why doesn't the comma throw an error?
> 
> 
> plot(1:5,)    # works, no complaints
> 
> 
> Shouldn't this be considered a bug? I would expect the parser to at least give a warning.
> 
> 
> sessionInfo()
> R version 4.2.1 (2022-06-23 ucrt)
> Platform: x86_64-w64-mingw32/x64 (64-bit)
> Running under: Windows 10 x64 (build 22000)
> 
> Matrix products: default
> 
> locale:
> [1] LC_COLLATE=Portuguese_Portugal.utf8 LC_CTYPE=Portuguese_Portugal.utf8
> [3] LC_MONETARY=Portuguese_Portugal.utf8 LC_NUMERIC=C 
> [5] LC_TIME=Portuguese_Portugal.utf8
> 
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
> 
> loaded via a namespace (and not attached):
> [1] compiler_4.2.1
> 
> 
> Rui Barradas
> 
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-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd.mes using cbs.dk  Priv: PDalgd using gmail.com