fact: Fixpoint Tdepth e:= match e with | Tbase _ => 0 | Tpowerset e' => (Tdepth e').+1 | Tproduct e' e'' => (maxn (Tdepth e') (Tdepth e'')).+1 end.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq)