fact: Fixpoint Tree_value E e:= match e with | Tbase n => Vg E (nat_to_B n) | Tpowerset e' => \Po (Tree_value E e') | Tproduct e' e'' => (Tree_value E e') \times (Tree_value E e'') end.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat) mathcomp(seq)