On Thu, Aug 30, 2018 at 10:58 AM Martin Maechler
<maech...@stat.math.ethz.ch> wrote:
>
> >>>>> Joris Meys
> >>>>> on Thu, 30 Aug 2018 14:48:01 +0200 writes:
>
> > On Thu, Aug 30, 2018 at 2:09 PM Dénes Tóth
> > <toth.de...@kogentum.hu> wrote:
> >> Note that `||` and `&&` have never been symmetric:
> >>
> >> TRUE || stop() # returns TRUE stop() || TRUE # returns an
> >> error
> >>
> >>
> > Fair point. So the suggestion would be to check whether x
> > is of length 1 and whether y is of length 1 only when
> > needed. I.e.
>
> > c(TRUE,FALSE) || TRUE
>
> > would give an error and
>
> > TRUE || c(TRUE, FALSE)
>
> > would pass.
>
> > Thought about it a bit more, and I can't come up with a
> > use case where the first line must pass. So if the short
> > circuiting remains and the extra check only gives a small
> > performance penalty, adding the error could indeed make
> > some bugs more obvious.
>
> I agree "in theory".
> Thank you, Henrik, for bringing it up!
>
> In practice I think we should start having a warning signalled.
> I have checked the source code in the mean time, and the check
> is really very cheap
> { because it can/should be done after checking isNumber(): so
> then we know we have an atomic and can use XLENGTH() }
>
>
> The 0-length case I don't think we should change as I do find
> NA (is logical!) to be an appropriate logical answer.
Can you explain your reasoning a bit more here? I'd like to understand
the general principle, because from my perspective it's more
parsimonious to say that the inputs to || and && must be length 1,
rather than to say that inputs could be length 0 or length 1, and in
the length 0 case they are replaced with NA.
Hadley
--
http://hadley.nz
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