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  1. #include <iostream>
  2. #include <typeinfo>
  3. #include <cstdint>
  4.  
  5. template <class T>
  6. constexpr T pwrtwo(T exponent) {
  7.   return (T(1) << exponent);
  8. }
  9.  
  10. template <class T>
  11. constexpr T pwrtwo_nocast(T exponent) {
  12.   return (1 << exponent);
  13. }
  14.  
  15. int main()
  16. {
  17.   uint8_t u8 = 7;
  18.   uint16_t u16 = 15;
  19.   uint32_t u32 = 31;
  20.   uint64_t u64 = 63;
  21.  
  22.   std::cout << "sizeof(int) is " << sizeof(int) << std::endl;
  23.  
  24.   std::cout << "no cast:\n"
  25.             << "uint8_t: " << uint64_t(pwrtwo_nocast(u8)) << "\n"
  26.             << "uint16_t: " << pwrtwo_nocast(u16) << "\n"
  27.             << "uint32_t: " << pwrtwo_nocast(u32) << "\n"
  28.             << "uint64_t: " << pwrtwo_nocast(u64) << "\n\n"
  29.             << "cast:\n"
  30.             << "uint8_t: " << uint64_t(pwrtwo(u8)) << "\n"
  31.             << "uint16_t: " << pwrtwo(u16) << "\n"
  32.             << "uint32_t: " << pwrtwo(u32) << "\n"
  33.             << "uint64_t: " << pwrtwo(u64) << std::endl;
  34. }
  35.  
Success #stdin #stdout 0s 3456KB
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stdin
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Standard input is empty
stdout
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sizeof(int) is 4
no cast:
uint8_t: 128
uint16_t: 32768
uint32_t: 2147483648
uint64_t: 0

cast:
uint8_t: 128
uint16_t: 32768
uint32_t: 2147483648
uint64_t: 9223372036854775808
https://ideone.com/z5GGvS
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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