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  1. #include <iostream>
  2. #include <utility>
  3. #include <map>
  4. #include <list>
  5. struct Asteroid {};
  6. typedef std::list<Asteroid> list_t;
  7. typedef list_t::iterator iter_t;
  8. typedef std::pair<iter_t, iter_t> pair_t;
  9. struct Comp {
  10.     bool operator()(const pair_t& p1, const pair_t& p2) const { 
  11.            return &*p1.first < &*p2.first ? true : 
  12.                   &*p2.first < &*p1.first ? false : 
  13.                   &*p1.second < &*p2.second; // won't handle the end iterators!
  14.     }
  15. };
  16. int main()
  17. {
  18.     list_t l;
  19.     l.push_back(Asteroid());
  20.     l.push_back(Asteroid());
  21.     l.push_back(Asteroid());
  22.  
  23.     std::map<pair_t, double, Comp> m;
  24.     m[make_pair(l.begin(), l.begin())] = 3.14;
  25.     m[make_pair(l.begin(), std::next(l.begin()))] = 3.14;
  26.     m[make_pair(l.begin(), l.begin())] = 3.14;
  27.  
  28.     std::cout << "Map has " << m.size() << " elements\n";
  29. }
Success #stdin #stdout 0s 2964KB
comments (?)
stdin
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Standard input is empty
stdout
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Map has 2 elements
https://ideone.com/oHpt5
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
public

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