#8800: Doctest coverage of categories
--------------------------+-------------------------------------------------
Reporter: SimonKing | Owner: Simon King
Type: defect | Status: new
Priority: major | Milestone: sage-4.4.1
Component: categories | Keywords: categories doctests
Author: Simon King | Upstream: N/A
Reviewer: | Merged:
Work_issues: |
--------------------------+-------------------------------------------------
Comment(by SimonKing):
I think it would be better to base this ticket on #8807, since I believe
that #8807 should be merged soon anyway.
Continuing with the doc tests, I think I found another bug, namely in the
``merge`` method of the Quotient construction functor:
{{{
sage: Q15,R = (ZZ.quo(15*ZZ)).construction()
sage: Q15
QuotientFunctor
sage: Q35,R = (ZZ.quo(35*ZZ)).construction()
sage: Q35
QuotientFunctor
sage: Q15.merge(Q35) is None
True
sage: from sage.categories.pushout import pushout
sage: pushout(ZZ.quo(15*ZZ),ZZ.quo(35*ZZ))
---------------------------------------------------------------------------
CoercionException Traceback (most recent call
last)
/home/SimonKing/<ipython console> in <module>()
/usr/local/sage/local/lib/python2.6/site-
packages/sage/categories/pushout.pyc in pushout(R, S)
1099 else:
1100 # Otherwise, we cannot proceed.
-> 1101 raise CoercionException, ("Ambiguous
Base Extension", R, S)
1102
1103 return all(Z)
CoercionException: ('Ambiguous Base Extension', Ring of integers modulo
15, Ring of integers modulo 35)
}}}
The reason is that internally ``Q35.I + Q15.I`` is tried, but this raises
an error. It works with ``Q35.I.gcd(Q15.I)``, though. If I do this (in a
patch that I will hopefully post in a few days, one gets (as one
''should'', if I am not mistaken)
{{{
sage: pushout(ZZ.quo(15*ZZ),ZZ.quo(35*ZZ))
Ring of integers modulo 5
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/8800#comment:7>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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