(* Simultaneous evaluation of a list of expressions *)
Fixpoint list_eval (es:list expr) (vs:list val) : pred world :=
match es, vs with
| e::es', v::vs' => eval e v && list_eval es' vs'
| nil, nil => TT
| _, _ => FF
end.

(* List evaluation likewise passes into larger worlds. *)
Lemma list_eval_up : forall es vals P Q,
(P && list_eval es vals) * Q |--
(P * Q) && list_eval es vals.