Re: help: derived class uses base class protect value

Hi Group:
  I just come to a confusion thing which is different from what my text
book says.
The code is below:

//************************************
class Base
{
protected:
   int mutex;
};

class Foo : public Base
{
public:
  inline void bar(int v) { mutex = v;}
};
//***************************************
compiled result is:

foo.h: In function `void bar()':
foo.h:33: error: `mutex' undeclared (first use this function)
foo.h:33: error: (Each undeclared identifier is reported only once for
each function it appears in.)
//***************************************
To my surprise, the code won't be compiled. The compiler(gcc) says the
variable mutex didn't be declared. However the text book told me the
derived class could see the Base class' protected thing through public
derived, didn't it?

could someone give me any suggestion?