Function: mssplit
Section: modular_forms
C-Name: mssplit
Prototype: GG
Help: mssplit(M,H): M being a full modular symbol space, as given by msinit,
 and H being a subspace, split H into Hecke-simple subspaces.
Doc:
 $M$ being a full modular symbol space, as given by \kbd{msinit}$(N,k,1)$
 or $\kbd{msinit}(N,k,-1)$
 and $H$ being a Hecke-stable subspace of \kbd{msnew}$(M)$, split $H$ into
 Hecke-simple subspaces.
 A subspace is given by a structure allowing quick projection and restriction
 of linear operators; its first component is a matrix with integer
 coefficients whose columns form a $\Q$-basis of the subspace.
 \bprog
 ? M = msinit(11,8, 1); \\ M_8(Gamma_0(11))^+
 ? L = mssplit(M, msnew(M));
 ? #L
 %3 = 2
 ? f = msqexpansion(M,L[1],5); f[1].mod
 %4 = x^2 + 8*x - 44
 ? lift(f)
 %5 = [1, x, -6*x - 27, -8*x - 84, 20*x - 155]
 ? g = msqexpansion(M,L[2],5); g[1].mod
 %6 = x^4 - 558*x^2 + 140*x + 51744
 @eprog\noindent To a Hecke-simple subspace corresponds an orbit of
 (normalized) newforms, defined over a number field. In the above example,
 we printed the polynomials defining the said fields, as well as the first
 5 Fourier coefficients (at the infinite cusp) of one such form.
