为什么Scala具有路径依赖类型？

Question

I've been doing some research on path-dependent types. The best description I could find for it was:

If L is a type label, then xL and yL are the same type iff x and y can be shown to refer to the same object.

This sometimes isn't the subtyping behaviour one would expect. I would expect that if L in the above example was indeed identical then that would be enough to make xL and yL indentical.

Is there any particular reason why Scala was designed this way?

Answer 1

可扩展组件抽象论文对路径依赖类型有很好的解释，也是第3节中的一个很好的例子：“案例研究：主题/观察者”。

Answer 2

This paper explains it nicely. Basically, they're used to support abstract data type based programming and modularization.

Answer 3

Think about L as about type argument of generic class. Scala boasts about its type members but underlying JVM still has the same limitations.