ismith takes as argument a matrix with coefficients in
ℤ.
ismith returns three matrices U,B and V such
that B=U*A*V, U and V are invertible in ℤ,
B is diagonal, and B[i,i] divides B[i+1,i+1].
The coefficients B[i,i] are called
invariant factors, they are used to describe
the structure of finite abelian groups.
Input :
Output :
The invariant factors are 3, 12 and 60.