--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/prepaper/src/agda-term3.agda	Tue Dec 08 19:06:49 2020 +0900
@@ -0,0 +1,12 @@
++-comm : (x y : ℕ) → x + y ≡ y + x
++-comm zero y rewrite (+zero {y}) = refl
++-comm (suc x) y = let open ≡-Reasoning in
+  begin
+  suc (x + y) ≡⟨⟩
+  suc (x + y) ≡⟨ cong suc (+-comm x y) ⟩
+  suc (y + x) ≡⟨ sym (+-suc {y} {x}) ⟩
+  y + suc x ∎
+
+-- +-suc : {x y : ℕ} → x + suc y ≡ suc (x + y)
+-- +-suc {zero} {y} = refl
+-- +-suc {suc x} {y} = cong suc (+-suc {x} {y})