#18478: Fix comparison of equal newforms in different parents
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Reporter: pbruin | Owner:
Type: defect | Status: new
Priority: minor | Milestone: sage-6.8
Component: modular forms | Keywords: newform comparison
Merged in: | Authors: Peter Bruin
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
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Two newforms that are identical but live in different parents (spaces of
cusp forms for `Gamma0` versus `Gamma1`, or with versus without character)
should be regarded as equal, but currently are not:
{{{
sage: f = Newforms(Gamma1(11), 2)[0]; f
q - 2*q^2 - q^3 + 2*q^4 + q^5 + O(q^6)
sage: g = Newforms(Gamma0(11), 2)[0]; g
q - 2*q^2 - q^3 + 2*q^4 + q^5 + O(q^6)
sage: f == g
False
}}}
{{{
sage: f = Newforms(DirichletGroup(4)[1], 5)[0]; f
q - 4*q^2 + 16*q^4 - 14*q^5 + O(q^6)
sage: g = Newforms(Gamma1(4), 5)[0]; g
q - 4*q^2 + 16*q^4 - 14*q^5 + O(q^6)
sage: f == g
False
}}}
This came up in comment:15:ticket:18061. The current version of the
`__eq__` method was written in #18068; I did not know about this bug then.
Comparison of modular forms of type `ModularFormElement` living in
different parents is broken as well (see e.g. comment:9:ticket:18068), but
this should probably dealt with on a different ticket, by properly
implementing coercion for modular forms.
--
Ticket URL: <http://trac.sagemath.org/ticket/18478>
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