I suspect that the parser used it to store comments, including the initial
"#", before R started using the srcref attribute. (S also stored comments
in the parse tree.)
Bill Dunlap
TIBCO Software
wdunlap tibco.com
On Tue, Nov 12, 2019 at 4:16 PM Duncan Murdoch <murdoch.dun...@gmail.com>
wrote:
> On 12/11/2019 5:01 p.m., William Dunlap via R-devel wrote:
> > In general R doesn't print the "comment" attribute of an object
> > > structure(1:3, comment=c("a comment", "another comment"))
> > [1] 1 2 3
> > but if the object is a call it prints it in an unusual format
> > > structure(quote(func(arg)), comment=c("a comment", "another
> comment"))
> > a comment
> > another comment
> > func(arg)
> >
> > What is the rationale for the special treatment of calls?
>
> It was there in revision 2 of src/main/deparse.c in 1997. (For those
> unfamiliar with R history: the current revision of R is 77405. That
> particular file has been revised 248 times since rev 2.)
>
> I suspect either nobody has noticed it before, or nobody had the nerve
> to touch it.
>
> Duncan Murdoch
>
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