On Fri, Sep 18, 2015, at 14:24, Terry Reedy wrote: > If a, b, c are members of a totally ordered set, so that < is > transitive, this is equivalent to max(a,c) < b. But the latter makes an > irrelevant comparison between a and c.
But *who would write that?* It's not a natural form of notation. I'm not saying it doesn't mean anything in Python. Obviously everything that is allowed means something. I'm saying no-one would write that in an ordinary context of human communication and expect to be understood. > > Your claim seemed to be that these combinations *are* > > used, since you claimed that python implements the *same* semantics. > > The semantics Python copies from math is "a op b op c == a op b and b op > c", I don't believe those *are* the semantics in math. I believe that in math this notation is *specifically* meant to support "all of these things are related to all of the others in ways that can be summarized in a single expression" and that mixing operations in a way that does not allow that is a misuse of the notation. In other words, any "a op b op c" that does not allow you to make a statement on how a is related to c is a *mistake*, because it means that you're welding together two things that aren't logically connected to each other at all. If there is no operator op3 where a op1 b op2 c implies a op3 c, then you should not put a and c in the same inequality, full stop. > where 'op' is a binary predicate or comparison operator. I also > happen to believe you are wrong in the specific examples. But the > semantic copying would apply even if a particular combination had not > yet ever been used. -- https://mail.python.org/mailman/listinfo/python-list
