proposition: Lemma checksubsum_set2 n n1 n2 (n1n2 : n1 != n2) (d : 'rV_n) : \delta [set n1; n2] d = (d ``_ n1 == d ``_ n2).
proof: Proof. rewrite /checksubsum big_setU1 ?inE //= big_set1. by rewrite -{1}(oppr_char2 (@char_Fp 2 erefl) (d ``_ n2)) subr_eq0. Qed.
imports: mathcomp(all_ssreflect ssralg fingroup finalg perm zmodp) mathcomp(matrix vector) Reals ssralg_ext ssrR Reals_ext f2 fdist channel tanner linearcode pproba