fact: Fixpoint app_no (t : term) : nat := match t with | Const _ | Id _ => 0 | Abs t => app_no t | App t1 t2 => 1 + (app_no t1 + app_no t2) end.
imports: mathcomp(ssreflect ssrbool eqtype) Arith List String Lia Program Relations Wellfounded Lexicographic_Product QuickChick(QuickChick) QuickChick.stlc(monad)