#18487: float and CombinatorialFreeModule
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Reporter: chapoton | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.10
Component: algebra | Resolution:
Keywords: float free module | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Changes (by tscrim):
* milestone: sage-6.8 => sage-6.10
Comment:
My guess is that the coercion framework is not working correctly with this
(from the `_acted_upon_` method of the CFM element):
{{{#!python
# With the current design, the coercion model does not have
# enough information to detect a priori that this method only
# accepts scalars; so it tries on some elements(), and we need
# to make sure to report an error.
if isinstance(scalar, Element) and scalar.parent() is not
self.base_ring():
# Temporary needed by coercion (see Polynomial/FractionField
tests).
if self.base_ring().has_coerce_map_from(scalar.parent()):
scalar = self.base_ring()( scalar )
else:
return None
}}}
and not doing the (correct) pushout construction. Thus it is not
constructing the correct parent. I also get this:
{{{
sage: C = CombinatorialFreeModule(ZZ,['a','b','c'])
sage: C.basis()['a'] * (2/3)
...
TypeError: unsupported operand parent(s) for '*': 'Free module generated
by {'a', 'b', 'c'} over Integer Ring' and 'Rational Field'
}}}
I don't think the cause is the above snippet, but I suspect it is further
down with the construction functor for CFM's (or really lack thereof).
Compare with:
{{{
sage: C.construction()
sage: M = ZZ^3
sage: 3.12 * M([1,0,0])
(3.12000000000000, 0.000000000000000, 0.000000000000000)
sage: _.parent()
Vector space of dimension 3 over Real Field with 53 bits of precision
sage: M.construction()
(VectorFunctor, Integer Ring)
}}}
--
Ticket URL: <http://trac.sagemath.org/ticket/18487#comment:2>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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