fact: Definition cols_starblank (M : 'M[letter]_(m, n)) (s : {set 'I_n}) := forall n0, n0 \in s -> col n0 M = \col_m0 (if m0 \in 'F n0 then Star else Blank).
imports: mathcomp(all_ssreflect ssralg fingroup finalg perm zmodp) mathcomp(matrix) f2 ssr_ext ssralg_ext max_subset num_occ hamming ldpc_erasure tanner linearcode