fact: Definition card_ball q n r := (\sum_(i < r.+1) 'C(n, i) * (q.-1)^i)%N.
imports: mathcomp(all_ssreflect ssralg poly polydiv fingroup perm) mathcomp(finalg zmodp matrix mxalgebra mxpoly vector) ssr_ext ssralg_ext poly_ext f2 hamming decoding channel_code