#18263: reintroduce `__neg__` for magmas cartesian product
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Reporter: vdelecroix | Owner:
Type: defect | Status: needs_review
Priority: major | Milestone: sage-6.7
Component: categories | Resolution:
Keywords: | Merged in:
Authors: Vincent Delecroix | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/vdelecroix/18263 | af11981fecdeb91b886b21962626d7ae7d720a65
Dependencies: #16836 | Stopgaps:
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Changes (by {'newvalue': u'Vincent Delecroix', 'oldvalue': ''}):
* status: new => needs_review
* commit: => af11981fecdeb91b886b21962626d7ae7d720a65
* branch: => u/vdelecroix/18263
* author: => Vincent Delecroix
Old description:
> In #16836 the `__neg__` operation for cartesian product was moved from
> `AdditiveMagmas` to the `AdditiveMagmas.WithInverse()`. The operation was
> ambiguous but the feature is lost. We just revert the removal.
>
> Moreover, there was a bug in Cartesian products of
> `CombinatorialFreeModule` as this generic `__neg__` was called instead of
> the customized `_neg_` which worked (see
> [http://trac.sagemath.org/ticket/16836#comment:22 #16836 comment:22] and
> [http://trac.sagemath.org/ticket/16836#comment:23 #16836 comment:23])!
> One solution is to use `__neg__` everywhere instead of `_neg_`.
New description:
In #16836 the `__neg__` operation for cartesian product was moved from
`AdditiveMagmas` to the `AdditiveMagmas.WithInverse()`. The operation was
ambiguous but the feature is lost. We just revert the removal.
Moreover, there was a bug in Cartesian products of
`CombinatorialFreeModule` as this generic `__neg__` was called instead of
the customized `_neg_` which worked (see
[http://trac.sagemath.org/ticket/16836#comment:22 #16836 comment:22] and
[http://trac.sagemath.org/ticket/16836#comment:23 #16836 comment:23])! We
replace `_neg_` with `__neg__` in `CombinatorialFreeModule`.
--
Comment:
New commits:
||[http://git.sagemath.org/sage.git/commit/?id=6e9cf9e72ced0969fd920eca5437f2e3c1d33009
6e9cf9e]||{{{Ticket 16836 fix __neg__ for cartesian products}}}||
||[http://git.sagemath.org/sage.git/commit/?id=af11981fecdeb91b886b21962626d7ae7d720a65
af11981]||{{{Trac 18263: __neg__}}}||
--
Ticket URL: <http://trac.sagemath.org/ticket/18263#comment:2>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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