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  1. #include <iostream>
  2. using namespace std;
  3. class bar {
  4. public: 
  5.     void change_it() {}  
  6.     void read_it() const {} 
  7. }; 
  8. class foo {
  9. public:
  10. 	bar A() const {   // const function
  11.     	return m_var; 
  12. 	}
  13. 	bar const B() {   // non const function, but const return type
  14.     	return m_var; 
  15. 	}
  16. 	bar const& C() const {   // non const function, but const reference return type
  17.     	return m_var; 
  18. 	}
  19. //private:
  20. 	bar m_var; 
  21. };
  22.  
  23. int main() {
  24. 	const foo x{}; 
  25. 	x.A();                // ok 
  26. 	//x.B();              // not ok -> function B() doesn't guarantee to leave x unchanged. 
  27. 	x.C();                // ok 
  28.     const bar& y = x.C(); // ok  (y will not alter m_var).
  29.     //int& z = x.C();       // not ok since z is not const 
  30.  
  31.     foo u{}; 
  32.     u.B();                // ok 
  33.     u.B().read_it();      // ok
  34.     //u.B().change_it();    // not ok because of const return value.  
  35.  
  36. 	return 0;
  37. }
Success #stdin #stdout 0s 15232KB
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https://ideone.com/4xGDZA
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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