[ python-Bugs-1633648 ] incomplete numerical comparisons

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Bugs item #1633648, was opened at 2007-01-11 19:18
Message generated for change (Comment added) made by rhettinger
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Category: Python Interpreter Core
Group: Python 2.5
Status: Open
Resolution: None
>Priority: 6
Private: No
Submitted By: Matthias Klose (doko)
Assigned to: Nobody/Anonymous (nobody)
Summary: incomplete numerical comparisons

Initial Comment:
[forwarded from http://bugs.debian.org/334022]

bug submitter writes:

I've been tracking down the regression failure in python-pgsql under
python2.[45], and here's what it comes down to.

Python-pgsql includes a short int type named PgInt2, which allows itself
to be coerced into all of the usual numeric types.

The regression that fails is when a PgInt2 is compared with a float.  In
this case python determines that the comparison is not implemented.

The problem is this:

- Under python2.[45], the float type includes tp_richcompare but not
  tp_compare.

- When calling try_rich_to_3way_compare(), python does not try any kind
  of numeric coercion, and so the comparison fails.

- When calling try_3way_compare(), python successfully coerces the
  PgInt2 into a float, but then the comparison fails because the float
  type has no tp_compare routine.

Presumably what would fix things would be one of the following:

- Bring back the trivial float_compare() routine, which was removed with
  python2.[45] when they brought in the new float_richcompare() instead;

- In try_3way_compare(), if the coercion succeeds and neither object
  has a tp_compare routine, try tp_richcompare before failing completely.

Does either of these solutions seem feasible?

Thanks - Ben.


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>Comment By: Raymond Hettinger (rhettinger)
Date: 2007-04-11 11:55

Message:
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Raising the priority so this report doesn't get lost.

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