On Nov 13, 2009, at 2:47 PM, Duncan Murdoch wrote:
> Inconsistent with what happens for lists:
>
> > x <- list()
> > x$b
> NULL
>
> and attributes:
>
> > attr(x, "b")
> NULL
Ah, I see. I would claim that the same argument for default safety should apply
here too.
> It is already a little stricter than $ on a list:
>
> > x$longname <- 1
> > x$long
> [1] 1
> > e$longname <- 1
> > e$long
> NULL
I apologize that I cannot say that this is a good idea for reasons of safety
and readability.
> so I supposed we could make it even more strict, but there is an awful lot of
> code out there that uses tests like
>
> if (!is.null(x <- e$b)) { do something with x }
>
> and all of that would break.
Unfortunately, such code does make it harder to detect programming errors.
I understand should the hands of R be tied by backwards-compatability; bad
habits are hard to break.
Thanks for your time.
-Trishank
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