Gamma、Richard Helm、Ralph Johnson 和 John Vlissides（Addison-Wesley Professional, 1994）编写的书 Design Patterns: Elements of Reusable Object-Oriented Software ，通称 The Gang of Four，是一本面向对象设计模式的目录。它这样定义面向对象编 程： Object-oriented `({integer}, {integer}, {integer})` | | | expected a tuple with 3 elements, found one with 2 elements | = note: expected tuple `({integer}, {integer}, {integer})` found