Re: True == 1 weirdness

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Subject	Re: True == 1 weirdness
Date	Fri, 18 Sep 2015 15:12:38 -0400
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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.

Thread

Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-18 08:47 -0400
  Re: True == 1 weirdness Steven D'Aprano <steve@pearwood.info> - 2015-09-18 23:14 +1000
    Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-18 09:40 -0400
      Re: True == 1 weirdness Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2015-09-19 19:19 +1200
    Re: True == 1 weirdness Terry Reedy <tjreedy@udel.edu> - 2015-09-18 14:24 -0400
    Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-18 15:12 -0400
      Re: True == 1 weirdness Jussi Piitulainen <harvesting@makes.email.invalid> - 2015-09-19 09:23 +0300
    Re: True == 1 weirdness Ian Kelly <ian.g.kelly@gmail.com> - 2015-09-18 15:13 -0600
    Re: True == 1 weirdness Random832 <random832@fastmail.com> - 2015-09-18 17:21 -0400

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