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  1. #include <type_traits>
  2. #include <iostream>
  3. using namespace std;
  4.  
  5. template<typename T, typename ...U>
  6.  auto time_function(T&& func, U&& ...args) 
  7.     -> typename enable_if<is_same<decltype(func(args...)), void>::value>::type
  8. {
  9.     std::cout<<"timing void function"<<std::endl;
  10.     std::forward<T>(func)(std::forward<U>(args)...);
  11.  
  12.     std::cout<<"timing over"<<std::endl;
  13. }
  14.  
  15. template<typename T, typename ...U>
  16. auto time_function(T&& func, U&& ...args)
  17.  -> typename enable_if<!is_same<decltype(func(args...)), void>::value, decltype(func(args...))>::type
  18. {
  19.     std::cout<<"timing returning function"<<std::endl;
  20.     auto val = std::forward<T>(func)(std::forward<U>(args)...);
  21.  
  22.     std::cout<<"timing over"<<std::endl;
  23.  
  24.     return val;
  25. }
  26.  
  27.  
  28. void foo(int){}
  29. int foo_return(int){return 0;}
  30.  
  31. int main()
  32. {
  33.  
  34.     time_function(foo, 2);
  35.     int i = time_function(&foo_return, 1); //this generates an error
  36.     std::cout<<i<<std::endl;
  37.  
  38. }
Success #stdin #stdout 0s 4372KB
comments (?)
stdin 
Standard input is empty
stdout 
timing void function
timing over
timing returning function
timing over
0
https://ideone.com/UZH9wU
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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