In the g+ + compiler environment , as defined in the following form class ?

class AAA: public :: BBB :: CCC :: DDD {
.....
};

BBB, CCC, DDD refers to what ?

DDD should be a class , BBB and CCC is the name space or something else , when it will use this defined.
------ Solution ---------------------------------------- ----

是继承了嵌套类中的类，形如：
  class BBB
  {
  public:
  	class CCC
  	{
  	public :
  		class DDD
  		{
  			......
  		};
  	};
  };
  
  class AAA : public ::BBB::CCC::DDD
  {
  .....
  };

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never seen such a frustrating
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very common normal syntax .