Symbolic interval matrix power

[schillic]

#83 suggests to reformulate the matrix power with explicit intervals.

When interpreting an interval matrix M as a set of matrices Aᵢ, and we only require that

M^k ⊇ ⋃ᵢ Aᵢ^k

holds, we can do better: Perform the multiplications symbolically: e.g., in 2D, consider M = [a b; c d] and write M^k as a matrix whose entries are polynomials in the original intervals a,b,c,d. Then in the end evaluate the final polynomials with interval arithmetic.