We have a class in Chicago asking for civil engineers to teach them how to build a bridge. In Idaho, a class is asking for a scientist to help them build a working river delta inside their classroom.
Scala makes it possible to reuse the new member definitions of a class (i.e. the delta in relationship to the superclass) in the definition of a new class.
Scala允许定义新类的时候重用“一个类中新增的成员定义（即相较于其父类的差异之处）”。
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Other rockets of this class, such as Boeing’s Delta IV and the Atlas V, operated jointly by Boeing and Lockheed Martin, are children of the military-industrial complex.