fork download
copy 
  1. #include <iostream>
  2. #include <bitset>
  3.  
  4. std::bitset<4> flag_out(int f) {
  5.     return std::bitset<4>(f);
  6. }
  7.  
  8. #include <climits>
  9. // For CHAR_BIT.
  10. #include <cstdint>
  11. // For uint8_t.
  12.  
  13. // Underlying flag type.  Change as needed.  Should remain unsigned.
  14. typedef uint8_t flag_t;
  15.  
  16. // Helper functions, to provide cleaner syntax to the enum.
  17. // Not actually necessary, they'll be evaluated at compile time either way.
  18. constexpr flag_t flag(int f) {
  19.     return 1 << f;
  20. }
  21. constexpr flag_t fl_validate(int f) {
  22.     return (f ? (1 << f) + fl_validate(f - 1) : 1);
  23. }
  24. constexpr flag_t register_invalids(int f) {
  25.     return static_cast<flag_t>(-1) - fl_validate(f - 1);
  26. }
  27.  
  28. // List of available flags.
  29. enum BitFlag : flag_t {
  30.     FFalse   = flag(0),  // 0001
  31.     FTrue    = flag(1),  // 0010
  32.     FDefault = flag(2),  // 0100
  33.     FToggle  = flag(3),  // 1000
  34.  
  35.     // ...
  36.  
  37.     // Number of defined flags.
  38.     FLAG_COUNT = 4,
  39.     // Indicator for invalid flags.
  40.     FLAG_INVALID = register_invalids(FLAG_COUNT),
  41.     // Maximum number of available flags.
  42.     FLAG_MAX = sizeof(flag_t) * CHAR_BIT
  43. };
  44.  
  45. void func(flag_t f) {
  46.     if (f & FLAG_INVALID) throw "Invalid flags, yo!";
  47.     if (f & FFalse)   std::cout << "Flag: FFalse." << std::endl;
  48.     if (f & FTrue)    std::cout << "Flag: FTrue." << std::endl;
  49.     if (f & FDefault) std::cout << "Flag: FDefault." << std::endl;
  50.     if (f & FToggle)  std::cout << "Flag: FToggle." << std::endl;
  51.     std::cout << std::endl;
  52. }
  53.  
  54. int main() {
  55.     std::cout << "False: " << flag_out(FFalse) << '\n'
  56.               << "True: " << flag_out(FTrue) << '\n'
  57.               << "Default: " << flag_out(FDefault) << '\n'
  58.               << "Toggle: " << flag_out(FToggle) << '\n'
  59.               << "False + True: " << flag_out(FFalse | FTrue) << '\n'
  60.               << "False + Default: " << flag_out(FFalse | FDefault) << '\n'
  61.               << "False + Toggle: " << flag_out(FFalse | FToggle) << '\n'
  62.               << "True + Default: " << flag_out(FTrue | FDefault) << '\n'
  63.               << "True + Toggle: " << flag_out(FTrue | FToggle) << '\n'
  64.               << "Default + Toggle: " << flag_out(FDefault | FToggle) << '\n'
  65.               << "False + True + Default: " << flag_out(FFalse | FTrue | FDefault) << '\n'
  66.               << "False + True + Toggle: " << flag_out(FFalse | FTrue | FToggle) << '\n'
  67.               << "True + Default + Toggle: " << flag_out(FTrue | FDefault | FToggle) << '\n'
  68.               << "All four: " << flag_out(FFalse | FTrue | FDefault | FToggle) << std::endl << std::endl;
  69.  
  70.     func(FFalse);
  71.     func(FFalse | FTrue);
  72.     func(FFalse | FDefault);
  73.     func(FFalse | FToggle);
  74.     func(FFalse | FTrue | FDefault);
  75.     func(FFalse | FTrue | FToggle);
  76.     func(FFalse | FDefault | FToggle);
  77.     func(FFalse | FTrue | FDefault | FToggle);
  78.     func(FTrue);
  79.     func(FTrue | FDefault);
  80.     func(FTrue | FToggle);
  81.     func(FTrue | FDefault | FToggle);
  82.     func(FDefault);
  83.     func(FDefault | FToggle);
  84.     func(FToggle);
  85.  
  86.     std::cout << "Invalid flags: " << std::bitset<8>(FLAG_INVALID) << std::endl;
  87.  
  88.  
  89.     try {
  90.         func(16);
  91.     } catch (const char* p) {
  92.         std::cout << p << std::endl;
  93.     }
  94. }
Success #stdin #stdout 0s 3416KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
False: 0001
True: 0010
Default: 0100
Toggle: 1000
False + True: 0011
False + Default: 0101
False + Toggle: 1001
True + Default: 0110
True + Toggle: 1010
Default + Toggle: 1100
False + True + Default: 0111
False + True + Toggle: 1011
True + Default + Toggle: 1110
All four: 1111

Flag: FFalse.

Flag: FFalse.
Flag: FTrue.

Flag: FFalse.
Flag: FDefault.

Flag: FFalse.
Flag: FToggle.

Flag: FFalse.
Flag: FTrue.
Flag: FDefault.

Flag: FFalse.
Flag: FTrue.
Flag: FToggle.

Flag: FFalse.
Flag: FDefault.
Flag: FToggle.

Flag: FFalse.
Flag: FTrue.
Flag: FDefault.
Flag: FToggle.

Flag: FTrue.

Flag: FTrue.
Flag: FDefault.

Flag: FTrue.
Flag: FToggle.

Flag: FTrue.
Flag: FDefault.
Flag: FToggle.

Flag: FDefault.

Flag: FDefault.
Flag: FToggle.

Flag: FToggle.

Invalid flags: 11110000
Invalid flags, yo!
https://ideone.com/I90HPT
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
secret

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!