Question

// By using structure :     
struct complex {
  float real;
  float imag;
};    

complex operator+(complex, complex);    

main() { 
  complex t1, t2, t3;    
  t3 = t1 + t2;    
}    

complex operator+(complex w, complex z) {
  statement 1;    
  statement 2;   
}    

// By using class :    
class complex {
  int real;
  int imag;    

public:    
  complex operator+(complex c) {
    statement 1;    
    statement 2;    
  }    

  main() {    
    complex t1, t2, t3;    
    t3 = t1 + t2;    
  }    

While using structure, the overloaded function can accept two arguments whereas while using class the overloaded function accepts only one argument, when the overloaded operator function is a member function in both cases i.e in struct as well as in class. Why does this happen?

Answer 1

…when the overloaded operator function is a member function in both
cases i.e structure as well as class…

What makes you say that? That’s not true.

In case of struct in your example, overloaded operator function is not a member. This is why it requires 2 parameters.

So, the difference has absolutely nothing to do with struct vs. class matter. The reason you have different number of parameters in these operators is that the first one is implemented as a non-member (and therefore has two explicit parameters), while the second one is implemented as member (and therefore has only one explicit parameter).