(datatype Math (Add Math Math) (Lit i64))

(birewrite (Add (Add x y) z) (Add x (Add y z)))

(let a (Lit 1))
(let b (Lit 2))
(let c (Lit 3))

(let d (Lit 4))
(let e (Lit 5))
(let f (Lit 6))

(let ex1 (Add (Add a b) c))
(let ex2 (Add d (Add e f)))

(run 10)
(check (= ex1 (Add a (Add b c))))
(check (= ex2 (Add (Add d e) f)))