Actually, sum(), all(), any(), prod() all return a _carefully considered_ result in the case of an empty vector. The sum over a disjoint union of sets should be the sum of the sums over each set, so if a set is empty, its contribution to the sum must be zero. Similarly, the product over an empty set is 1. Logical aggregate all() should be stable for "&" and any() for "|", hence all(logical(0))==TRUE and any(logical(0))==FALSE.
-pd > On 16 Jan 2023, at 16:53 , GILLIBERT, Andre <andre.gillib...@chu-rouen.fr> > wrote: > > Duncan Murdoch <murdoch.dun...@gmail.com> wrote: > >> To even do that, we would have to first decide which "cases" should produce >> a warning. > >> Let's say `1 + x` should give a warning when x = numeric(0). Then should >> `x^2` also produce a warning? Should `x^0.5`? Should `sqrt(x)`? >> Should `log(x)`? > > > The most probable errors would be in functions taking two arguments (e.g. > `+`) and for which one argument has length >= 2 while the other has length 0. > > In my experience, most code with accidental zero-length propagations (e.g. > typo in data_frame$field) quickly lead to errors, that are easy to debug > (except for beginners), and so, do not need a warning. > > The only cases where zero-length propagation is really dangerous in my > experience is in code using an aggregating function like sum(), all() or > any(), because it silently returns a valid value for a zero-length argument. > Emitting warnings for sum(numeric(0)) would probably have too many false > positives but a (length >= 2) vs (length == 0) warning for common binary > operators could sometimes catch the issue before it reaches the aggregating > function. > > -- > Sincerely > André GILLIBERT > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Office: A 4.23 Email: pd....@cbs.dk Priv: pda...@gmail.com ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
