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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Tue, 11 Nov 2014 10:59:00 -0700
Subject: Re: "Natural" use of cmp= in sort
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Xref: csiph.com comp.lang.python:80548

On Tue, Nov 11, 2014 at 2:21 AM, Paddy <paddy3118@gmail.com> wrote:
> On Tuesday, 11 November 2014 09:07:14 UTC, Ian  wrote:
>> On Tue, Nov 11, 2014 at 12:44 AM, Paddy <paddyxxx-at-xmail.com> wrote:
>> > Thanks Ian. The original author states "...and it is sure that the giv=
en inputs will give an output, i.e., the inputs will always be valid.", whi=
ch could be taken as meaning that all inputs are sufficient, well formed, a=
nd contain all relations as their first example does.
>>
>> Well, I brought it up because the start of that sentence is "There can
>> be multiple inequalities as answer but I need any one which is
>> correct...". The only way there would be more than one correct answer
>> would be if the inputs were only partially ordered. I take the second
>> part of the sentence as meaning only that the input can be safely
>> assumed to be consistent.
>>
>> > Yes, I knew that there are cases where a cmp function is more natural =
than key; the idea is to squirrel out a few. We have already made the, (wel=
l reasoned in my opinion), decision to go down the key=3D route in Python 3=
. I also like to track where my algorithms might originally map to cmp=3D. =
(It is not often).
>>
>> Basically any time you have a comparison that isn't easily expressed
>> by mapping the values to some bunch of ordered objects.
>
> Yep. I want to track when this comes up for me and others during their no=
rmal programming rather than in examples made to highlight the issue.

The example that I posted is one that I recall being brought up on
this list in the past, but I don't have a link for you.