[Python-3000] Total ordering and cmp (original) (raw)

Guido van Rossum guido at python.org
Wed Mar 21 03:46:28 CET 2007

But can this work? It might end up calling cmp() on two incomparable objects. For lt etc. that might be the right answer, but for eq it is not -- the default eq and ne must compare object identity.

(What is this __cmp you refer to? A typo for cmp or for cmp?)

--Guido

On 3/20/07, Terry Reedy <tjreedy at udel.edu> wrote:

"Collin Winter" <collinw at gmail.com> wrote in message news:43aa6ff70703201810p9d731b8v3497a48539d5dc84 at mail.gmail.com... | Quoting from the commit message for r51533, which removed the default ordering: | | What's the status on this? FWIW, I would like to see cmp stay as a | fallback measure if eq, ne, lt, etc aren't defined for | total ordering purposes. I've run across this while trying to get the | docs toolchain working, and I was initially shocked that cmp was | no longer called. An alternative would be to give the object class comparison methods defined _in terms of a missing cmp() method. _def eq(self,other): return cmp(self,other) == 0 # etc This would put the fallback to and conversion of cmp -1,0,1 output in one place instead of sprinkled everywhere. Or these could go into a cmporder mixin put in some lib module. Terry Jan Reedy

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-- --Guido van Rossum (home page: http://www.python.org/~guido/)

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