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  1.     #include <iostream>
  2.     struct CallIntDelegate
  3.     {
  4.         virtual void operator()(int i) const = 0;
  5.     };
  6.  
  7.     template<typename O, void (O::*func)(int)>
  8.     struct IntCaller : public CallIntDelegate
  9.     {
  10.         IntCaller(O* obj) : object(obj) {}
  11.         void operator()(int i) const
  12.         {
  13.             // This line can easily optimized by the compiler
  14.             // in object->func(i) (= normal function call, not pointer-to-member call)
  15.             // Pointer-to-member calls are slower than regular function calls
  16.             (object->*func)(i);
  17.         }
  18.     private:
  19.         O* object;
  20.     };
  21.  
  22.     void set(const CallIntDelegate& setValue)
  23.     {
  24.         setValue(42);
  25.     }
  26.  
  27.     class test
  28.     {
  29.     public:
  30.         void printAnswer(int i)
  31.         {
  32.             std::cout << "The answer is " << 2 * i << "\n";
  33.         }
  34.     };
  35.  
  36.     int main()
  37.     {
  38.         test obj;
  39.         set(IntCaller<test,&test::printAnswer>(&obj));
  40.     }
Success #stdin #stdout 0.01s 2680KB
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stdin
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Standard input is empty
stdout
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The answer is 84
https://ideone.com/IrRzeD
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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