// An alternative approach: using a 'using type alias'. C++11

#include <vector>

int x = 5;

template<typename T>double f(){
  using it = typename T::iterator;      // a 'using type alias'
  it *x;                                // A simpel and plain declaration: x is of type it* 
                    

  // ...
}

int main(){
  f<std::vector<double>>();             // >> is OK in C++11
                                        
}