On Tue, Jul 10, 2007 at 10:36:55AM -0400, Alan G Isaac wrote: > I found Gael's presentation rather puzzling for two reasons.
> 1. It appears to contain a `+` vs. `*` confusion. > See http://en.wikipedia.org/wiki/Two-element_Boolean_algebra Damn it. I used math conventions, for "+" and "*" (in math the "+" law of a ring is the law for which every element has an inverse). I hadn't realized it was the opposite for intuitive understanding of booleans. > 2. MUCH more importantly: > In implementations of TWO, we interpret `-` as unary > complementation (not e.g. as additive inverse; note True > does not have one). Yes, indeed, as the law for which every element has an inverse is "*", the inverse for the "+" is not defined, and therefore the "-" sign cannot design it. You are quite right that it is impossible to define "-" on the boolean set in a way that makes it follow tradition integer operations. I don't know what the conclusion of this should be in terms of the original discussion. Sorry for the noise. Gaël _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
