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  1. #include <istream>
  2. #include <ostream>
  3. #include <iostream>
  4. #include <type_traits>
  5. #include <cstdint>
  6.  
  7. #define ENABLE_IF_INTEGRAL(T)\
  8. typename = typename std::enable_if<std::is_integral<std::decay_t<T>>::value>::type
  9.  
  10. namespace detail{
  11.     template<class T, ENABLE_IF_INTEGRAL(T)>
  12.     struct wrapper{
  13.         T& x;
  14.         wrapper(T& xx) : x(xx){};
  15.  
  16.         friend std::istream& operator >> (std::istream& is, wrapper<T> w){
  17.             auto read = +w.x;
  18.             is>>read;
  19.             w.x = static_cast<std::decay_t<T>>(read);
  20.             if(w.x != read)
  21.                 is.setstate(std::ios::failbit);
  22.             return is;
  23.         }
  24.     };
  25. }
  26.  
  27. template<class T, ENABLE_IF_INTEGRAL(T)>
  28. auto intoInt(T& x){ return detail::wrapper<T>(x);}
  29.  
  30. template<class T, ENABLE_IF_INTEGRAL(T)>
  31. auto asInt(T x){ return +x; }
  32.  
  33.  
  34. #undef ENABLE_IF_INTEGRAL    
  35.  
  36. int main() {
  37.     char foo;
  38.  
  39.     std::cin>>intoInt(foo);
  40.  
  41.     std::cout<< (std::cin.fail() ? "failed":"success")<<std::endl;
  42.  
  43. 	std::cout << asInt(foo) << '\n';
  44.  
  45.     return 0;
  46. }
Success #stdin #stdout 0s 3472KB
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https://ideone.com/U6bhlk
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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