Function: algprimesubalg
Section: algebras
C-Name: algprimesubalg
Prototype: G
Help: algprimesubalg(al): prime subalgebra of the positive characteristic,
 semisimple algebra al.
Doc: \var{al} being the output of \tet{algtableinit} representing a semisimple
 algebra of positive characteristic, returns a basis of the prime subalgebra
 of~\var{al}. The prime subalgebra of~\var{al} is the subalgebra fixed by the
 Frobenius automorphism of the center of \var{al}. It is abstractly isomorphic
 to a product of copies of $\F_p$.
 \bprog
 ? mt = [matid(3), [0,0,0; 1,1,0; 0,0,0], [0,0,1; 0,0,0; 1,0,1]];
 ? A = algtableinit(mt,2);
 ? algprimesubalg(A)
 %3 =
 [1 0]

 [0 1]

 [0 0]
 @eprog
