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  1. #include <iostream>
  2.  
  3. // Version 1: (return type fixed)
  4.  
  5. class Complex1 {
  6.   friend std::ostream& operator << (std::ostream &out, const Complex1 &c);
  7.   private:
  8.     int a;
  9.   public:
  10.     explicit Complex1(int a): a(a) { }
  11.     // operator + as member
  12.     Complex1 operator + (const Complex1 &c) const
  13.     {
  14.       return Complex1(a + c.a);
  15.     }
  16. };
  17.  
  18. std::ostream& operator << (std::ostream &out, const Complex1 &c)
  19. {
  20.   return out << c.a;
  21. }
  22.  
  23. // Version 2: (two overloaded operators)
  24.  
  25. class Complex2 {
  26.   friend std::ostream& operator << (std::ostream &out, const Complex2 &c);
  27.   friend int operator+(const Complex2 &c, const Complex2 &d);
  28.   friend int operator+(int c, const Complex2 &d);
  29.   private:
  30.     int a;
  31.   public:
  32.     explicit Complex2(int a): a(a) { }
  33.  
  34. };
  35.  
  36. std::ostream& operator << (std::ostream &out, const Complex2 &c)
  37. {
  38.   return out << c.a;
  39. }
  40.  
  41. int operator+(const Complex2 &c, const Complex2 &d)
  42. {
  43.   return c.a + d.a;
  44. }
  45.  
  46. int operator+(int c, const Complex2 &d)
  47. {
  48.   return c + d.a;
  49. }
  50.  
  51. // Version 3: (implicit conversion with constructor)
  52.  
  53. class Complex3 {
  54.   friend std::ostream& operator << (std::ostream &out, const Complex3 &c);
  55.   private:
  56.     int a;
  57.   public:
  58.     Complex3(int a): a(a) { }
  59.     // operator + as member
  60.     int operator+(const Complex3 &c) const
  61.     {
  62.       return a + c.a;
  63.     }
  64. };
  65.  
  66. std::ostream& operator << (std::ostream &out, const Complex3 &c)
  67. {
  68.   return out << c.a;
  69. }
  70.  
  71. // Check everything out:
  72.  
  73. using namespace std;
  74.  
  75. int main()
  76. {
  77.   cout << "Version 1:" << endl;
  78.   { Complex1 c1(3), c2(5), c3(2);
  79.     Complex1 c4 = c1 + c2 + c3;
  80.     cout << "c4: " << c4 << endl;
  81.   }
  82.   cout << "Version 2:" << endl;
  83.   { Complex2 c1(3), c2(5), c3(2);
  84.     Complex2 c4 = Complex2(c1 + c2 + c3);
  85.     cout << "c4: " << c4 << endl;
  86.   }
  87.   cout << "Version 3:" << endl;
  88.   { Complex1 c1(3), c2(5), c3(2);
  89.     Complex1 c4 = c1 + c2 + c3;
  90.     cout << "c4: " << c4 << endl;
  91.   }
  92.   cout << "done." << endl;
  93.   return 0;
  94. }
  95.  
Success #stdin #stdout 0s 16048KB
comments (?)
stdin
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Standard input is empty
stdout
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Version 1:
c4: 10
Version 2:
c4: 10
Version 3:
c4: 10
done.
https://ideone.com/aPVSgx
language:
C++ (gcc 8.3)
created:
8 years ago
visibility:
public

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