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  1. // Copyright 2017 <Biagio Festa>
  2. #include <iostream>
  3. #include <type_traits>
  4.  
  5. struct CriticalError : std::true_type {
  6.   static constexpr bool is_critical = true;
  7. };
  8.  
  9. struct Warning : std::false_type {
  10.   static constexpr bool is_critical = false;
  11. };
  12.  
  13. template<typename ErrorPolicy>
  14. void foo() {
  15.   if constexpr (ErrorPolicy::is_critical) {
  16.       std::cout << "Critical\n";
  17.     } else {
  18.     std::cout << "NotCritical\n";
  19.   }
  20.  
  21.   if constexpr (std::is_base_of<std::true_type, ErrorPolicy>::value) {
  22.       std::cout << "Critical\n";
  23.     } else {
  24.     std::cout << "NotCritical\n";
  25.   }
  26.   // ...
  27. }
  28.  
  29. int main(int argc, char *argv[]) {
  30.   foo<CriticalError>();
  31.   foo<Warning>();
  32.   return 0;
  33. }
  34.  
Success #stdin #stdout 0s 15240KB
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stdin
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Standard input is empty
stdout
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Critical
Critical
NotCritical
NotCritical
https://ideone.com/aUo5Pa
language:
C++14 (clang 8.0)
created:
6 years ago
visibility:
public

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