On 04/01/2016 11:09 AM, Lukas Stadler wrote:> Hi,
>
> maybe there?s a reason for it, but the discrepancy between the handling of
`[` and `$` in deparsing seems odd to me:
> > substitute(a[1], list(a = quote(x * y)))
> x * y[1]
> > substitute(a$b, list(a = quote(x * y)))
> (x * y)$b
>
> The former is still executed in the right order (`*` first, then `[`),
which is not what you?d expect looking at the deparse result.
> Some code that shows the execution order:
> x <- 1; y <- 1; class(y) <- "foo"; `*.foo` <-
function(...) -1; expr <- substitute(a[1], list(a=quote(x * y)));
list(expr=expr, eval=eval(expr), "x * y[1]"=x * y[1], "(x *
y)[1]"=(x * y)[1])
>
> The following simple fix solves the problem for me:
>
> diff -u -r A/src/main/deparse.c B/src/main/deparse.c
> --- R-devel 2/src/main/deparse.c 2015-08-09 18:09:04.000000000 +0200
> +++ R-devel/src/main/deparse.c 2016-01-04 16:15:09.000000000 +0100
> @@ -971,7 +971,11 @@
> print2buff(")", d);
> break;
> case PP_SUBSET:
> + if ((parens = needsparens(fop, CAR(s), 1)))
> + print2buff("(", d);
> deparse2buff(CAR(s), d);
> + if (parens)
> + print2buff(")", d);
> if (PRIMVAL(SYMVALUE(op)) == 1)
> print2buff("[", d);
> else
>
> With this applied, the output is more consistent:
> > substitute(a[1], list(a = quote(x * y)))
> (x * y)[1]
> > substitute(a$b, list(a = quote(x * y)))
> (x * y)$b
No reason, just a bug. I'll fix it.
Duncan Murdoch