Definition prog_c : com :=
  SKIP.Definition prog_g : com :=
  WHILE BTrue DO
    SKIP
  END.Definition equiv_classes : list (list com)
  (* REPLACE THIS LINE WITH ":= _your_definition_ ." *).

Lemma sym_aequiv : forall (a1 a2 : aexp), aequiv a1 a2 -> aequiv a2 a1.