| trans_exp env vartypes (A.OpExp(oper, [e1, e2])) =
T.BINOP(trans_oper oper, trans_exp env vartypes e1, trans_exp env vartypes e2)
| trans_exp env vartypes (A.OpExp(oper, [e])) =
| trans_exp env vartypes (A.OpExp(oper, [e1, e2])) =
T.BINOP(trans_oper oper, trans_exp env vartypes e1, trans_exp env vartypes e2)
| trans_exp env vartypes (A.OpExp(oper, [e])) =