fact: Definition decode_const (n : nat) : const := match n with 0 => Zero | 1 => One | n.+2 => URoot n end.
imports: HB(structures) mathcomp(all_ssreflect all_fingroup all_algebra) mathcomp(all_solvable all_field polyrcf) Abel(various classic_ext map_gal algR) Abel(char0 cyclotomic_ext real_closed_ext)