#12969: Coercion failures in symmetric functions
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Reporter: aschilling | Owner: sage-combinat
Type: defect | Status: new
Priority: major | Milestone: sage-5.3
Component: combinatorics | Resolution:
Keywords: symmetric functions, coercion | Work issues:
Report Upstream: N/A | Reviewers:
Authors: | Merged in:
Dependencies: | Stopgaps:
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Comment (by SimonKing):
Observation: When starting with your example, one gets
{{{
sage: from sage.structure.element import get_coercion_model
sage: cm = get_coercion_model()
sage: Ht.has_coerce_map_from(P)
False
sage: cm.discover_coercion(P,Ht)
(None, Composite map:
From: Macdonald polynomials in the Ht basis over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field
To: Macdonald polynomials in the P basis over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field
Defn: Composite map:
From: Macdonald polynomials in the Ht basis over Fraction Field
of Multivariate Polynomial Ring in q, t over Rational Field
To: Macdonald polynomials in the J basis over Fraction Field
of Multivariate Polynomial Ring in q, t over Rational Field
Defn: Generic morphism:
From: Macdonald polynomials in the Ht basis over
Fraction Field of Multivariate Polynomial Ring in q, t over Rational Field
To: Symmetric Function Algebra over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field, Schur symmetric
functions as basis
then
Generic morphism:
From: Symmetric Function Algebra over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field, Schur symmetric
functions as basis
To: Macdonald polynomials in the J basis over Fraction
Field of Multivariate Polynomial Ring in q, t over Rational Field
then
Generic morphism:
From: Macdonald polynomials in the J basis over Fraction Field
of Multivariate Polynomial Ring in q, t over Rational Field
To: Macdonald polynomials in the P basis over Fraction Field
of Multivariate Polynomial Ring in q, t over Rational Field)
sage: Ht.has_coerce_map_from(P)
False
sage: cm.discover_coercion(Ht,P)
(Composite map:
From: Macdonald polynomials in the Ht basis over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field
To: Macdonald polynomials in the P basis over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field
Defn: Composite map:
From: Macdonald polynomials in the Ht basis over Fraction Field
of Multivariate Polynomial Ring in q, t over Rational Field
To: Macdonald polynomials in the J basis over Fraction Field
of Multivariate Polynomial Ring in q, t over Rational Field
Defn: Generic morphism:
From: Macdonald polynomials in the Ht basis over
Fraction Field of Multivariate Polynomial Ring in q, t over Rational Field
To: Symmetric Function Algebra over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field, Schur symmetric
functions as basis
then
Generic morphism:
From: Symmetric Function Algebra over Fraction Field of
Multivariate Polynomial Ring in q, t over Rational Field, Schur symmetric
functions as basis
To: Macdonald polynomials in the J basis over Fraction
Field of Multivariate Polynomial Ring in q, t over Rational Field
then
Generic morphism:
From: Macdonald polynomials in the J basis over Fraction Field
of Multivariate Polynomial Ring in q, t over Rational Field
To: Macdonald polynomials in the P basis over Fraction Field
of Multivariate Polynomial Ring in q, t over Rational Field, None)
sage: Ht.has_coerce_map_from(P)
False
}}}
Thus, apparently the problem is that "coerce_map_from" does not call
discover_coercion when it should. Broken cache, apparently. Non-unique
parents?
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/12969#comment:4>
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