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  1. #include <vector>
  2. #include <string>
  3. #include <list>
  4. #include <type_traits>
  5. #include <iostream>
  6. #include <iterator>
  7.  
  8. using T = std::string;
  9. using VectT = std::vector<T>;
  10. using ListT = std::list<VectT>;
  11.  
  12. using value_type = T;
  13.  
  14. class const_iterator :
  15.     public std::iterator<std::bidirectional_iterator_tag , value_type const> {
  16. public:
  17.     using ListIt = typename ListT::const_iterator;
  18.     using VectIt = typename VectT::const_iterator;
  19.  
  20.     explicit const_iterator(ListIt itHigh, VectIt itLow) :
  21.         itHigh_{itHigh}, itLow_{itLow} {
  22.     }
  23.  
  24.     const_iterator(const const_iterator &it) :
  25.         itHigh_{it.itHigh_}, itLow_{it.itLow_} {
  26.     }
  27.  
  28.     const_iterator & operator ++ () {
  29.         std::cout << "increment" << std::endl;
  30.         itLow_++;
  31.         if (itLow_ == itHigh_->end()) {
  32.             itHigh_++;
  33.             itLow_ = itHigh_->begin();
  34.         }
  35.  
  36.         return *this;
  37.     }
  38.  
  39.     const_iterator operator ++ (int) {
  40.         const_iterator retval = *this;
  41.  
  42.         ++(*this);
  43.  
  44.         return retval;
  45.     }
  46.  
  47.     const_iterator & operator -- () {
  48.         std::cout << "decrement" << std::endl;
  49.         itLow_--;
  50.         if (itLow_ == --itHigh_->begin()) {
  51.             itHigh_--;
  52.             itLow_ = --(itHigh_->end());
  53.         }
  54.  
  55.         return *this;
  56.     }
  57.  
  58.     const_iterator operator -- (int) {
  59.         const_iterator retval = *this;
  60.  
  61.         --(*this);
  62.  
  63.         return retval;
  64.     }
  65.  
  66.     bool operator == (const_iterator other) const {
  67.         return other.itHigh_ == itHigh_&& other.itLow_ == itLow_;
  68.     }
  69.  
  70.     bool operator != (const_iterator other) const {
  71.         return !(other == *this);
  72.     }
  73.  
  74.     const value_type & operator * () const {
  75.         return *itLow_;
  76.     }
  77.  
  78.     const value_type * operator -> () const {
  79.         return &(operator *());
  80.     }
  81.  
  82. private:
  83.     ListIt itHigh_;
  84.     VectIt itLow_;
  85. };
  86.  
  87. int main() {
  88.     std::cout 
  89.         << std::is_same<typename std::iterator_traits<const_iterator>::value_type, std::string const>::value
  90.         << std::endl;
  91.  
  92.     ListT items = {{"First", "Second"}, {"Third", "Fourth"}, {"Fifth", "Sixth", "Seventh"}};
  93.  
  94.     const_iterator it{items.begin(), items.begin()->begin()};
  95.  
  96.     const_iterator end{items.end(), items.end()->begin()};
  97.  
  98.     for (; it != end; it++) {
  99.         std::cout << *it << " ";
  100.     }
  101.     std::cout << std::endl;
  102.  
  103.     using const_reverse_iterator = std::reverse_iterator<const_iterator>;
  104.  
  105.     const_reverse_iterator rit{const_iterator{(--items.end()), --items.rbegin()->rbegin().base()}};
  106.  
  107.     const_reverse_iterator rend{const_iterator{items.begin(), --items.rend()->end()}};
  108.  
  109.     /*for (; rit != rend; rit++) {
  110.         std::cout << *rit << " ";
  111.     }*/
  112.     rit--;
  113.     --rit;
  114.     rit++;
  115.     ++rit;
  116.     std::cout << *rit << std::endl;
  117.     *rit;
  118.     *rit;
  119.  
  120.     std::cout << std::endl;
  121. }
  122.  
Success #stdin #stdout 0s 15248KB
comments (?)
stdin
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Standard input is empty
stdout
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1
First increment
Second increment
Third increment
Fourth increment
Fifth increment
Sixth increment
Seventh increment

increment
increment
decrement
decrement
decrement
Sixth
decrement
decrement
https://ideone.com/sRDWav
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
public

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