If you have, for example, a routine that adds a certain amount of money to a bank account, obviously the post-condition of this routine is going to have to express that the new balance is related to the old balance.

• 例如，你用某个例程将一定数额的存款累加到一个银行帐户上，那么很明显，这个例程的后置条件必须表述当前余额和过去余额的关系。