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  1. #include <utility>
  2. #include <cstdio>
  3. #include <cmath>
  4.  
  5. template<typename Fn>
  6. class Action {
  7.     Fn* function_ptr;
  8.  
  9. public:
  10.     Action() noexcept : function_ptr(nullptr) {
  11.     }    
  12.     Action(std::nullptr_t) noexcept : function_ptr(nullptr) {
  13.     }    
  14.     Action(const Action& other) : function_ptr(other.function_ptr) {
  15.     }    
  16.     Action(Fn f) : function_ptr(f) {
  17.     }
  18.  
  19.     Action& operator=(const Action& other) {
  20.         return (function_ptr = other.function_ptr, *this);
  21.     }            
  22.     Action& operator=(std::nullptr_t ) {
  23.         return (function_ptr = nullptr, *this);
  24.     }    
  25.     Action& operator=(Fn f) {
  26.         return (function_ptr = f, *this);
  27.     }
  28.  
  29.     template<typename... Params>
  30.     auto operator()(Params&&... params) {
  31.         return function_ptr(std::forward<Params>(params)...);
  32.     }
  33. };
  34.  
  35. void test(int i) {
  36.     printf("The given parameter is: %d\n", i);
  37. }
  38.  
  39. int main() {
  40.     Action<decltype(printf)> pf_1;
  41.     pf_1 = nullptr;    
  42.     pf_1 = printf;
  43.  
  44.     Action<decltype(printf)> pf_2(pf_1);
  45.     pf_2("The value of Pi is: %.5f\n", M_PI);
  46.  
  47.     Action<decltype(test)> test_fn(test);
  48.     test_fn(12);
  49.  
  50.     return 0;
  51. }
Success #stdin #stdout 0s 16064KB
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stdin
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Standard input is empty
stdout
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The value of Pi is: 3.14159
The given parameter is: 12
https://ideone.com/AsNQdt
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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