#18756: Use coerce actions in the category framework
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Reporter: SimonKing | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.8
Component: coercion | Resolution:
Keywords: cython, coercion, actions, | Merged in:
categories | Reviewers:
Authors: | Work issues:
Report Upstream: N/A | Commit:
Branch: | Stopgaps:
Dependencies: |
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Changes (by SimonKing):
* component: algebra => coercion
* branch: u/SimonKing/combinatorial_free_module_cython_coercion =>
Comment:
The commit that I just pushed moves `CombinatorialFreeModule` to Cython
and lets it use `RingElement` and `_l/rmul_` instead of the current
approach to work around the coercion framework.
Note that an action only depends on the parents involved and is cached.
Hence, it is better faster to invoke the category framework to use the
action to do a multiplication, than to let `__mul__` decide on the
implementation of multiplication in each single instance. Hence, we should
NOT do
{{{
#!python
class Modules:
class ElementMethods:
def __mul__(self, other):
if self.base_ring().has_coerce_map_from(parent(other)):
# Bad case-by-case behaviour
return self._mul_(other)
return coercion_model.bin_op(self, other, operator.mul)
}}}
and its counterpart in `Magmas.ElementMethods`. Instead, one should have a
`ParentMethod` returning an action.
However, my plan is to first sanitise the code of `[Ring/Module]Element`:
1. A parent should be able to provide an action on ANY parent, including
itself.
2. The possibility to use any action should be implemented on the level of
`Element.__mul__` (similarly `Element.__add__` etc).
3. The only thing that `ModuleElement.__mul__` and `RingElement.__mul__`
should contribute is a short-cut. That's basically what is already done:
`ModuleElement.__mul__` treats python int in a special way, since I guess
the typecheck involved is faster than calling the `coercion_model`; and
`RingElement.__mul__` deals with the special case that the two elements
have identical parents, which again is faster than calling the
`coercion_model`.
--
Ticket URL: <http://trac.sagemath.org/ticket/18756#comment:13>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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