# Modular Forms over a Non-minimal Base Ring¶

class sage.modular.modform.ambient_R.ModularFormsAmbient_R(M, base_ring)

Ambient space of modular forms over a ring other than QQ.

EXAMPLES:

sage: M = ModularForms(23,2,base_ring=GF(7)) ## indirect doctest
sage: M
Modular Forms space of dimension 3 for Congruence Subgroup Gamma0(23) of weight 2 over Finite Field of size 7
True

change_ring(R)

Return this modular forms space with the base ring changed to the ring R.

EXAMPLES:

sage: chi = DirichletGroup(109, CyclotomicField(3)).0
sage: M9 = ModularForms(chi, 2, base_ring = CyclotomicField(9))
sage: M9.change_ring(CyclotomicField(15))
Modular Forms space of dimension 10, character [zeta3 + 1] and weight 2 over Cyclotomic Field of order 15 and degree 8
sage: M9.change_ring(QQ)
Traceback (most recent call last):
...
ValueError: Space cannot be defined over Rational Field

cuspidal_submodule()

Return the cuspidal subspace of this space.

EXAMPLES:

sage: C = CuspForms(7, 4, base_ring=CyclotomicField(5)) # indirect doctest
sage: type(C)
<class 'sage.modular.modform.cuspidal_submodule.CuspidalSubmodule_R_with_category'>

modular_symbols(sign=0)

Return the space of modular symbols attached to this space, with the given sign (default 0).