Design by Contract, or programming by Contract, is not a new concept in programming, many languages already having such implementations.

契约式设计(或“契约式编程”)并不是编程领域的新概念，许多语言中已经有类似的实现了。

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It also explains the difference between programming by contract and defensive programming with a clever situation where your customers request that the framework code do the checking.

该书还阐述了在客户请求框架代码进行检查的智能情况下，承包程序设计和防错性程序设计之间的差别。

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Design by Contract, or defensive programming.

契约式设计或防御性编程。

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