... Manual1
Copyright ©1995-2000 by Alex Aiken. All rights reserved. 
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... Nil.2
In this example, Nil is assumed to be a subtype of List. 
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... inheritance.''3
Some object-oriented languages allow a class to inherit from multiple classes, which is equally aptly called ``multiple inheritance.'' 
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... object.4
A shallow copy of $a$ copies $a$ itself, but does not recursively copy objects that $a$ points to. 
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...void.5
A tiny point: We are allowing void to be used as an expression here. There is no expression for void available to Cool programmers. 
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