Function: algalgtobasis
Section: algebras
C-Name: algalgtobasis
Prototype: GG
Help: algalgtobasis(al,x): transforms the element x of the algebra al into a
 column vector on the integral basis of al.
Doc: Given an element \var{x} in the central simple algebra \var{al} output
 by \tet{alginit}, transforms it to a column vector on the integral basis of
 \var{al}. This is the inverse function of \tet{algbasistoalg}.
 \bprog
 ? A = alginit(nfinit(y^2-5),[2,y]);
 ? algalgtobasis(A,[y,1]~)
 %2 = [0, 2, 0, -1, 2, 0, 0, 0]~
 ? algbasistoalg(A,algalgtobasis(A,[y,1]~))
 %3 = [Mod(Mod(y, y^2 - 5), x^2 - 2), 1]~
 @eprog
