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  1. #include <iostream>
  2.  
  3. template<std::uintmax_t, char...>
  4. struct strtoi_impl;
  5.  
  6. template<std::uintmax_t Rest, char Last>
  7. struct strtoi_impl<Rest, Last> {
  8.     static constexpr std::uintmax_t value = Rest + (Last - '0');
  9. };
  10.  
  11. template<std::uintmax_t Rest, char Head, char... Tail>
  12. struct strtoi_impl<Rest, Head, Tail...> {
  13.     static constexpr std::uintmax_t value = 
  14.         strtoi_impl<(Rest + (Head - '0')) * 10, Tail...>::value;
  15. };
  16.  
  17. template<char... Number>
  18. struct strtoi {
  19.     static constexpr std::uintmax_t value = 
  20.         strtoi_impl<0, Number...>::value;
  21. };
  22.  
  23. int main() 
  24. {
  25.     static_assert(strtoi<'1', '2', '3'>::value == 123, "no.");
  26. 	return 0;
  27. }
  28.  
Success #stdin #stdout 0s 3292KB
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https://ideone.com/9ZDdvG
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
secret

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