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  1. #include <iostream>
  2. using namespace std;
  3.  
  4. class ClassA; // Forward declaration
  5.  
  6. class ClassB; // Forward declaration
  7.  
  8. // Friend function declaration
  9. int sumPrivate(ClassA a, ClassB b);
  10.  
  11. class ClassA {
  12. private:
  13.     int numA;
  14.  
  15. public:
  16.     ClassA(int n) { numA = n; }
  17.  
  18.     // Declare friend function
  19.     friend int sumPrivate(ClassA a, ClassB b);
  20. };
  21.  
  22. class ClassB {
  23. private:
  24.     int numB;
  25.  
  26. public:
  27.     ClassB(int n) { numB = n; }
  28.  
  29.     // Declare friend function
  30.     friend int sumPrivate(ClassA a, ClassB b);
  31. };
  32.  
  33. // Friend function definition
  34. int sumPrivate(ClassA a, ClassB b) {
  35.     // Access private members of both classes
  36.     return a.numA + b.numB;
  37. }
  38.  
  39. int main() {
  40.     ClassA objA(10);
  41.     ClassB objB(20);
  42.  
  43.     cout << "Sum of private members: " << sumPrivate(objA, objB) << endl;
  44.  
  45.     return 0;
  46. }
  47.  
Success #stdin #stdout 0.01s 5316KB
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stdin
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Standard input is empty
stdout
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Sum of private members: 30
https://ideone.com/u6lfNH
language:
C++ (gcc 8.3)
created:
7 hours ago
visibility:
public

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