#9902: base_extend() not implemented in MPolynomialRing
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Reporter: vbraun | Owner: malb
Type: defect | Status: needs_info
Priority: major | Milestone: sage-4.6.1
Component: commutative algebra | Keywords:
Author: Volker Braun | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
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Changes (by novoselt):
* status: needs_review => needs_info
Comment:
I am not quite sure it is the right approach. It seems to me that we have
two methods: `change_ring` that constructs "the same object but over
different ring" and `base_extend` which does the same, but only if there
is a natural coercion. Given this description, it seems to me that there
should be only one implementation of `base_extend` in the base class:
{{{
def base_extend(self, R):
if R.has_coerce_map(self.base_ring()):
return self.change_ring(R)
else:
raise TypeError("%s cannot be extened to %s!" % (self.base_ring(),
R))
}}}
and then each derived class should implement `change_ring` only. (If the
detailed error message breaks a lot of doctests I am fine with keeping the
current one.) Thoughts?
There is also discrepancy between actual argument names and their
description in documentation (`base_ring` vs. `R`).
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/9902#comment:3>
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