fact: Definition simp_plus (e1 e2 : expr Nat) := match e1, e2 with | Const Nat n1, Const Nat n2 => Const Nat (n1 + n2) | _, Const Nat 0 => e1 | Const Nat 0, _ => e2 | _, _ => Plus e1 e2 end.
imports: Hammer(Tactics) Program.Equality Arith String