#19921: Handle zero coefficients when converting asymptotic rings
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Reporter: cheuberg | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-7.1
Component: asymptotic expansions | Resolution:
Keywords: | Merged in:
Authors: | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
Dependencies: | Stopgaps:
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Description changed by cheuberg:
Old description:
> {{{
> sage: sage: CR.<Z> = QQ['Z']
> sage: sage: CR_mod = CR.quotient((Z^2 - 1)*CR)
> sage: sage: R.<x> = AsymptoticRing(growth_group='x^NN',
> coefficient_ring=CR)
> /local/cheuberg/sage/sage-6.10/local/lib/python2.7/site-
> packages/sage/structure/unique_representation.py:1021: FutureWarning:
> This class/method/function is marked as experimental. It, its
> functionality or its interface might change without a formal deprecation.
> See http://trac.sagemath.org/17601 for details.
> instance = typecall(cls, *args, **options)
> sage: sage: R_mod =
> R.change_parameter(coefficient_ring=CR_mod)
> sage: sage: e = 1 + x*(Z^2-1)
> sage: sage: R_mod(e)
> Traceback (most recent call last):
> ...
> ValueError: Cannot include Z^2 - 1*x with parent Exact Term Monoid
> x^((Non negative integer semiring)) with coefficients in Univariate
> Polynomial Ring in Z over Rational Field in Asymptotic Ring <x^((Non
> negative integer semiring))> over Univariate Quotient Polynomial Ring in
> Zbar over Rational Field with modulus Z^2 - 1
> > *previous* ValueError: Zero coefficient 0 is not allowed in Exact Term
> Monoid x^((Non negative integer semiring)) with coefficients in
> Univariate Quotient Polynomial Ring in Zbar over Rational Field with
> modulus Z^2 - 1.
> }}}
New description:
{{{
sage: CR.<Z> = QQ['Z']
sage: CR_mod = CR.quotient((Z^2 - 1)*CR)
sage: R.<x> = AsymptoticRing(growth_group='x^NN', coefficient_ring=CR)
sage: R_mod = R.change_parameter(coefficient_ring=CR_mod)
sage: e = 1 + x*(Z^2-1)
sage: R_mod(e)
Traceback (most recent call last):
...
ValueError: Cannot include Z^2 - 1*x with parent Exact Term Monoid
x^((Non negative integer semiring)) with coefficients in Univariate
Polynomial Ring in Z over Rational Field in Asymptotic Ring
<x^((Non negative integer semiring))> over Univariate Quotient Polynomial
Ring in Zbar over Rational Field with modulus Z^2 - 1
> *previous* ValueError: Zero coefficient 0 is not allowed in Exact
Term Monoid x^((Non negative integer semiring)) with coefficients
in Univariate Quotient Polynomial Ring in Zbar over Rational Field
with modulus Z^2 - 1.
}}}
--
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Ticket URL: <http://trac.sagemath.org/ticket/19921#comment:1>
Sage <http://www.sagemath.org>
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