Function: algpow
Section: algebras
C-Name: algpow
Prototype: DGGG
Help: algpow({al},x,n): element x^n in al (Hamilton quaternions if omitted).
Doc: Given an element $x$ in \var{al} (Hamilton quaternions if omitted) and an
 integer $n$, computes the power $x^{n}$ in the algebra \var{al}.
 \bprog
 ? A = alginit(nfinit(y), [-1,-1]);
 ? algpow(A,[1,1,0,0]~,7)
 %2 = [8, -8, 0, 0]~
 ? algpow(,[1,2,3,sqrt(3)]~,-3) \\ Hamilton quaternions
 % = [-0.0095664563, 0.0052920822, 0.0079381233, 0.0045830776]~
 @eprog

 Also accepts a square matrix with coefficients in \var{al}.
