Function: alginv
Section: algebras
C-Name: alginv
Prototype: DGG
Help: alginv({al},x): element 1/x in al (Hamilton quaternions if omitted).
Doc: Given an element $x$ in \var{al} (Hamilton quaternions if omitted),
 computes its inverse $x^{-1}$ in the algebra \var{al}. Assumes that $x$ is
 invertible.
 \bprog
 ? A = alginit(nfinit(y), [-1,-1]);
 ? alginv(A,[1,1,0,0]~)
 %2 = [1/2, 1/2, 0, 0]~
 ? alginv(,[1,0,Pi,sqrt(2)]~) \\ Hamilton quaternions
 %3 = [0.0777024661, 0, -0.2441094967, -0.1098878814]~
 @eprog

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