fact: Definition ball q n x r := [set y : 'rV['F_q]_n | dH x y <= r].
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