On Fri, Dec 6, 2013 at 11:55 AM, Alexander Belopolsky <ndar...@mac.com> wrote: > > > > On Fri, Dec 6, 2013 at 1:46 PM, Alan G Isaac <alan.is...@gmail.com> wrote: >> >> On 12/6/2013 1:35 PM, josef.p...@gmail.com wrote: >> > unary versus binary minus >> >> Oh right; I consider binary `-` broken for >> Boolean arrays. (Sorry Alexander; I did not >> see your entire issue.) >> >> >> > I'd rather write ~ than unary - if that's what it is. >> >> I agree. So I have no objection to elimination >> of the `-`. > > > It looks like we are close to reaching a consensus on the following points: > > 1. * is well-defined on boolean arrays and may be used in preference of & in > code that is designed to handle 1s and 0s of any dtype in addition to > booleans. > > 2. + is defined consistently with * and the only issue is the absence of > additive inverse. This is not a problem as long as presence of - does not > suggest otherwise. > > 3. binary and unary minus should be deprecated because its use in > expressions where variables can be either boolean or numeric would lead to > subtle bugs. For example -x*y would produce different results from -(x*y) > depending on whether x is boolean or not. In all situations, ^ is > preferable to binary - and ~ is preferable to unary -. > > 4. changing boolean arithmetics to auto-promotion to int is precluded by a > significant use-case of boolean matrices.
+1 -- Nathaniel J. Smith Postdoctoral researcher - Informatics - University of Edinburgh http://vorpus.org _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
