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  1. #include <iostream>
  2.  
  3. struct A {
  4. 	struct APlusA {
  5. 		APlusA(const A&a_, const A&b_) : a(a_), b(b_) {}
  6. 		const A &a;
  7. 		const A &b;
  8.  
  9. 		operator A() const { 
  10. 			std::cout << "Creating temporary A" << std::endl; 
  11. 			return A(a.val + b.val);
  12. 		}
  13. 	};
  14.  
  15. 	A(int val_) : val(val_) {}
  16. 	friend APlusA operator+(const A&a, const A&b) { return APlusA(a,b); }
  17. 	friend std::ostream &operator<<(std::ostream &s, const A &a) { return s << a.val;}
  18.  
  19. 	A& operator=(const APlusA &apa) {
  20. 		if (this == &apa.a) {
  21. 			std::cout << "Performing in-place operator" << std::endl;
  22. 			val += apa.b.val;
  23. 		}
  24. 		else
  25. 		{
  26. 			*this = static_cast<A>(apa);
  27. 		}
  28. 	}
  29.  
  30. 	int val;
  31. };
  32.  
  33. int main() {
  34. 	A a(4), b(5), c(6);
  35. 	std::cout << a+b << std::endl; //Temporary created
  36. 	a = b+c;                       //Temporary created
  37. 	a = a+b;                       //No temporary - inplace operation
  38. 	std::cout << a << std::endl;
  39. 	return 0;
  40. }
  41.  
Success #stdin #stdout 0s 3140KB
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stdin
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Standard input is empty
stdout
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Creating temporary A
9
Creating temporary A
Performing in-place operator
16
https://ideone.com/ixypdo
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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