Local Open Scope option_monad_scope.
Fixpoint is_val_list (al: exprlist) : option (list (val * type)) :=
match al with
| Enil => Some nil
| Econs a1 al => do vt1 <- is_val a1; do vtl <- is_val_list al; Some(vt1::vtl)
end.
Definition is_skip (s: statement) : {s = Sskip} + {s <> Sskip}.

Lemma list_eventval_of_val_sound:
forall vl tl evl, list_eventval_of_val vl tl = Some evl -> eventval_list_match ge evl tl vl.