fact: Definition push_init down := if down is Some p then ([::p], p) else ([::], (1,1)).
imports: Init.Wf Recdef Reals mathcomp(all_ssreflect perm zmodp matrix ssralg) mathcomp(Rstruct) ssrR Reals_ext f2 subgraph_partition tanner fdist channel pproba linearcode ssralg_ext tanner_partition summary ldpc checksum