fact: Fixpoint max_arity (e : expr) (n : nat) := match e with | Evar k => Nat.ltb k n | Econst _ => true | Eunary o e1 => max_arity e1 n | Ebinary o e1 e2 => if max_arity e1 n then max_arity e2 n else false end.
imports: Coq(ZArith Reals List Psatz) Xreal Tree