Here is example:
class one {
    public:
    typedef someclass internal;
};
 
class two {
// No internal class
};
 
class default_internal{
};
 
I would like to be able to write something if it possible:
 
template<class T, class B = if_exist(T::internal)  T::internal else  default_internal > class proc {
};
 
So I can use proc with both
 
proc<one> One;
proc<two> Two;
 
without specifying derived type?
 
Thanks! \/.
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