tim_one at email.msn.com
Tue Mar 25 04:58:05 CET 2003
[David Mertz, Ph.D.]
> But the current list sorting behavior is BY FAR the most surprising
> thing in Python! I would have a big challenge explaining it to a new
> user... heck, I can hardly remember the border cases myself.
> The examples I gave in my first post for this thread show how surprising
> the exceptions are. I really think that more than half of highly
> experienced Python programmers would have gotten at least one of them
> wrong in their intuition (not you, not Alex... maybe not Guido :-)...
> but past that, mistakes).
I expect I would have gotten most of them wrong, and I confess I wasn't
interested enough to guess at what would happen. Why would I? I asked last
time what your use case is: for what purpose do you think you need to be
able to sort lists with a mix of element types for which Python can't dream
up a better ordering than comparing the objects' memory addresses? If you
don't have a real use case, I don't care about this.
> I guess part of what goes into this is different intuitions about the
> meaning of sorting. I put sorting a list into a different conceptual
> category than comparing individual items (while knowing, of course, the
> underlying relatedness of the concepts). Sorting, to me, just means a
> stable (but arbitrary) ordering. Comparison with "<" and friends
> implie, to me, a "natural" ordering. I wouldn't mind if "<" stopped
> comparing anything without an obviously correct answer.
What's your use case?
> Even then, no matter how you cut it, the relation "1j < 2j" is
> self-evident and natural. How can I explain to anyone why that is an
> error rather than a True result?!
It's like faith: if they know anything about complex numbers, no
explanation is necessary; if they don't know anything about complex numbers,
not only is no explanation possible, but they don't have a use case for it
either so it's not a real problem for them <0.5 wink>.
Since the members of a complex numbers are floats, then if 1j < 2j is
self-evident, what's the self-evident result for 1e-300+1j < 2j? Is one
self-evident and the other arbitrary? Etc. There are *useful* orderings on
complex numbers, but no "most useful" ordering, and no ordering at all is
conventionally defined on them.
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