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  1. #include <iostream>
  2. #include <map>
  3. #include <stdexcept>
  4.  
  5. template <typename K, typename V>
  6. V& map_at(std::map<K, V>& a_map, K const& a_key)
  7. {
  8.     typename std::map<K, V>::iterator i = a_map.find(a_key);
  9.     if (a_map.end() == i)
  10.     {
  11.         throw std::out_of_range("map_at()");
  12.     }
  13.     return i->second;
  14. }
  15.  
  16. int main()
  17. {
  18.     try
  19.     {
  20.         std::map<int, int> m;
  21.         m[4] = 4;
  22.         std::cout << map_at(m, 4) << std::endl;
  23.         map_at(m, 5);
  24.     }
  25.     catch (std::out_of_range const& e)
  26.     {
  27.         std::cout << "out_of_range: " << e.what() << std::endl;
  28.     }
  29.  
  30.     try
  31.     {
  32.         std::map<std::string, char> m;
  33.         m["hello"] = 'c';
  34.         std::cout << map_at(m, std::string("hello")) << std::endl;
  35.         map_at(m, std::string("world"));
  36.     }
  37.     catch (std::out_of_range const& e)
  38.     {
  39.         std::cout << "out_of_range: " << e.what() << std::endl;
  40.     }
  41.  
  42.     return 0;
  43. }
  44.  
Success #stdin #stdout 0s 3436KB
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4
out_of_range: map_at()
c
out_of_range: map_at()
https://ideone.com/lIkTD3
language:
C++ (gcc 8.3)
created:
10 years ago
visibility:
public

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