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  1. #include <string>
  2. #include <iostream>
  3. #include <utility>
  4. #include <iterator>
  5.  
  6.     template<class Mark, class T>
  7.     struct marked_type {
  8.       T raw;
  9.       marked_type(T&& in):raw(std::forward<T>(in)) {}
  10.     };
  11.     template<typename Mark, typename T>
  12.     marked_type<Mark, T> mark_type( T&& t ) {
  13.       return {std::forward<T>(t)};
  14.     }
  15.  
  16.     struct strange_iteration {};
  17.     template<typename T>
  18.     auto begin( marked_type<strange_iteration, T> const& container )
  19.       -> decltype( std::begin(std::forward<T>(container.raw)) )
  20.     {
  21.       std::cout << "BEGIN";
  22.       return std::begin(std::forward<T>(container.raw));
  23.     }
  24.     template<typename T>
  25.     auto end( marked_type<strange_iteration, T> const& container )
  26.       -> decltype( std::end(std::forward<T>(container.raw)) )
  27.     {
  28.       std::cout << "END";
  29.       return std::end(std::forward<T>(container.raw));
  30.     }        
  31. int main() {
  32.     std::string s = "hello world";
  33.     for( char c : mark_type<strange_iteration>(s) ) {
  34.       std::cout << c;
  35.     }
  36.     std::cout << "\n";
  37. }
Success #stdin #stdout 0s 3428KB
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stdin
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Standard input is empty
stdout
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BEGINENDhello world
https://ideone.com/RYvzD0
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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