Modular forms newform decomposition not implemented

[jonhanke]

sage: chi_tmp = DirichletGroup(105, RationalField())(kronecker_character_upside_down(105))
sage: MF = ModularForms(chi_tmp, 2)
sage: CF = MF.cuspidal_subspace()
sage: NF = CF.new_subspace()
sage: type(NF)
<class 'sage.modular.modform.submodule.ModularFormsSubmodule_with_category'>
sage: new_eigenform_list = NF.decomposition()
---------------------------------------------------------------------------
NotImplementedError                       Traceback (most recent call last)

/Users/jonhanke/Documents/SAGE/<ipython console> in <module>()

/Users/jonhanke/Documents/SAGE/sage-4.6/local/lib/python2.6/site-packages/sage/modular/modform/space.pyc in decomposition(self)
   1616             NotImplementedError
   1617         """
-> 1618         raise NotImplementedError
   1619
   1620     def newforms(self, names=None):

NotImplementedError:

CC: @williamstein @jonhanke @JohnCremona

Component: modular forms

Keywords: modular forms

Author: Jonathan Hanke

Issue created by migration from https://trac.sagemath.org/ticket/10806

[loefflerd]

comment:6

If you do

 sage.modular.hecke.HeckeModule_free_module.decomposition(NF) 

then it works (eventually -- it's way slower than it ought to be, but that's a separate issue).