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  1. #include <iostream>
  2. #include <vector>
  3. #include <list>
  4. #include <iterator>
  5. #include <typeinfo>
  6.  
  7. template <typename Iterator>
  8. class const_iterator
  9. {
  10.   public:
  11.     typedef Iterator                                                 iterator_type;
  12.     typedef typename std::iterator_traits<Iterator>::difference_type difference_type;
  13.     // note: trying to add const to ...:reference or ..:pointer doesn't work,
  14.     //       as it's like saying T* const rather than T const* aka const T*.
  15.     typedef const typename std::iterator_traits<Iterator>::value_type& reference;
  16.     typedef const typename std::iterator_traits<Iterator>::value_type* pointer;
  17.  
  18.     const_iterator(const Iterator& i) : i_(i) { }
  19.     reference operator*() const { return *i_; }
  20.     pointer operator->() const { return i_; }    
  21.     bool operator==(const const_iterator& rhs) const { return i_ == rhs.i_; }
  22.     bool operator!=(const const_iterator& rhs) const { return i_ != rhs.i_; }    
  23.     const_iterator& operator++() { ++i_; return *this; }
  24.     const_iterator operator++(int) const { Iterator i = i_; ++i_; return i; }
  25.   private:
  26.     Iterator i_;
  27. };
  28.  
  29. template <typename Const_Iterator>
  30. void f(const Const_Iterator& b__, const Const_Iterator& e__)
  31. {
  32. 	::const_iterator<Const_Iterator> b{b__}, e{e__};
  33. 	// *b = 2;  // if uncommented, compile-time error....
  34.     for ( ; b != e; ++b)
  35.         std::cout << *b << '\n';
  36. }
  37.  
  38. int main()
  39. {
  40.     std::vector<int> v { 11, 22, 33 };
  41.     f(v.begin(), v.end());
  42. }
Success #stdin #stdout 0s 3472KB
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Standard input is empty
stdout
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11
22
33
https://ideone.com/fAdDnO
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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