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  1. #include <iostream>
  2. #include <vector>
  3.  
  4. template <typename Range>
  5. class counted_view {
  6.     Range r;
  7.  
  8.     typedef counted_view self;
  9.  
  10.     typedef decltype(std::begin(r)) nested_iterator;
  11.     typedef decltype(*std::begin(r)) nested_value_type;
  12. public:
  13.  
  14.     counted_view(Range& r) : r(r) {}
  15.  
  16.     class iterator
  17.     {
  18.     public:
  19.         iterator(nested_iterator iter) : iter(iter), counter(0) {}
  20.  
  21.         std::pair<std::size_t, nested_value_type> operator*()
  22.         {
  23.             return std::pair<std::size_t, nested_value_type>(counter, *iter);
  24.         }
  25.  
  26.         iterator& operator++()
  27.         {
  28.             ++iter;
  29.             ++counter;
  30.  
  31.             return *this;
  32.         }
  33.  
  34.         bool operator!=(iterator& other)
  35.         {
  36.             return iter != other.iter;
  37.         }
  38.  
  39.     private:
  40.         nested_iterator iter;
  41.         std::size_t counter;
  42.     };
  43.  
  44.     iterator begin()
  45.     {
  46.  
  47.         return iterator(std::begin(r));
  48.     }
  49.  
  50.     iterator end()
  51.     {
  52.         return iterator(std::end(r));
  53.     }
  54. };
  55.  
  56. template <typename Range>
  57. counted_view<Range> counted(Range& r) {
  58.     return counted_view<Range>(r);
  59. }
  60.  
  61. int main(int argc, const char * argv[])
  62. {
  63.     std::vector<double> vec = {10,20,30,40,50,60,70,80,90};
  64.     for(auto p : counted(vec))
  65.     {
  66.         std::cout << p.first << ": " << p.second << std::endl;
  67.     }
  68.  
  69.     // insert code here...
  70.     std::cout << "Hello, World!\n";
  71.     return 0;
  72. }
  73.  
  74.  
Success #stdin #stdout 0s 3028KB
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stdin
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Standard input is empty
stdout
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0: 10
1: 20
2: 30
3: 40
4: 50
5: 60
6: 70
7: 80
8: 90
Hello, World!
https://ideone.com/zlqKs1
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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