#8402: Sanity check for Parents and Elements
------------------------------+---------------------------------------------
Reporter: hivert | Owner: hivert
Type: defect | Status: new
Priority: major | Milestone: sage-4.4
Component: categories | Keywords: Parent, Element, equality, zero,
one
Author: Florent Hivert | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
------------------------------+---------------------------------------------
Old description:
> Here is the summary of what was decided on
> [http://groups.google.com/group/sage-devel/t/5d9c32390ffe3c96
> sage=devel]:
>
> 1 - Any Parent or Element must have an equality methods such that
> {{{self == self}}} and {{{self != None}}}. This is not required for
> general {{{SageObject}}}.
>
> 2 - Element construction should be idempotent. More precisely, for any
> element e within parent P, the equality {{{P(e) == e}}} must hold.
>
> Case by case exception such as {{{RealIntervalField}}} are possible.
>
> 3 - element of a parent in the category {{{Monoid()}}} (respectively
> {{{CommutativeAdditiveMonoid()}}}) must have a {{{__hash__}}} method,
> which may raise an error for mutable element but never on {{{.one()}}}
> (respectively {{{.zero()}}})
New description:
Here is the summary of what was decided on [http://groups.google.com/group
/sage-devel/t/5d9c32390ffe3c96 sage=devel]:
1 - Any Parent or Element must have an equality methods such that
{{{self == self}}} and {{{self != None}}}. This is not required for
general {{{SageObject}}}. I also test that {{{self != self}}} and {{{self
== None}}} both returns {{{False}}}.
2 - Element construction should be idempotent. More precisely, for any
element e within parent P, the equality {{{P(e) == e}}} must hold. This
should only be enforced for true parent since it cause some problems for
facade parents.
Case by case exception such as {{{RealIntervalField}}} are possible.
3 - {{{_test_hash}}}: test that the result of hash is an int or that it
raises an appropriate exception
3' - element of a parent in the category {{{Monoid()}}} (respectively
{{{CommutativeAdditiveMonoid()}}}) must have a {{{__hash__}}} method,
which may raise an error for mutable element but never on {{{.one()}}}
(respectively {{{.zero()}}})
--
Comment(by hivert):
I'm preparing some patches on sage-combinat queue. I already caught some
bug with it: see #8695.
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8402#comment:2>
Sage <http://www.sagemath.org>
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