fact: Fixpoint Tree_to_echelon t := match t with | Tbase n => Ech_base (nat_to_B n.+1) | Tpowerset t' => Ech_powerset (Tree_to_echelon t') | Tproduct t' t'' => Ech_product (Tree_to_echelon t') (Tree_to_echelon t'') end.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq)