#813: forced coercion vs. automatic coercion
------------------------+---------------------------------------------------
Reporter: nbruin | Owner: roed
Type: defect | Status: new
Priority: major | Milestone: sage-4.7.1
Component: coercion | Keywords:
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
------------------------+---------------------------------------------------
Comment(by SimonKing):
PS: In addition, since there is a coercion from `QQ['y','x']` to
`QQ['x','y']`, it is conceivable that the pushout of `QQ['y','x']` with
`Frac(QQ['x'])['y']` should be `Frac(QQ['x'])['y']` as well. But it isn't:
{{{
sage: pushout(QQ['y','x'],Frac(QQ['x'])['y'])
---------------------------------------------------------------------------
CoercionException Traceback (most recent call
last)
/home/king/Projekte/MeatAxe/meataxe-2.2.4/<ipython console> in <module>()
/mnt/local/king/SAGE/sage-4.7.1.rc1/local/lib/python2.6/site-
packages/sage/categories/pushout.pyc in pushout(R, S)
3072 if Rc[-1] in Sc:
3073 if Sc[-1] in Rc:
-> 3074 raise CoercionException, ("Ambiguous
Base Extension", R, S)
3075 else:
3076 all = Sc.pop() * all
CoercionException: ('Ambiguous Base Extension', Multivariate Polynomial
Ring in y, x over Rational Field, Univariate Polynomial Ring in y over
Fraction Field of Univariate Polynomial Ring in x over Rational Field)
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/813#comment:9>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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