proposition: Lemma two_len : 2 < n.
proof: Proof. by rewrite len_dim -subn1 ltn_subRL (@leq_exp2l 2 2). Qed.
imports: mathcomp(all_ssreflect ssralg fingroup finalg perm zmodp) mathcomp(matrix mxalgebra vector) mathcomp(Rstruct) realType_ext ssr_ext ssralg_ext f2 linearcode natbin ssrR hamming bigop_ext fdist proba channel channel_code decoding binary_symmetric_channel