let u1 = mk_type_universe "1" in
E.add_lt_constraint ~acyclic:true u0 u1
-let fst_var = 1
+let fst_var = 1 (* first variable *)
-let snd_var = 2
+let snd_var = 2 (* second variable *)
+
+let fst_con = 1 (* first constructor *)
let appl ts = C.Appl ts