Class Operators

[ravpulp]

In the first Classes (II) example of C++ tutorial, the code shows an operator being defined (lines 18-23). The example shows one Cvector parameter (Cvector param), but in the main () function, two added values are passed as a variable to c (c=a+b). How is the operator taking these two values if it only takes one parameter under the operator + definition?

[Bazzy]

Because it's a member function. a + b is equivalent to a.operator + ( b )

[ravpulp]

Forgive my ignorance, could you explain that a little further. Not seeing what you mean.

[Bazzy]

Overloaded operators are just all other functions. Member operators have the this pointer as implicit argument.
Try to see if the following example helps:

#include <iostream>
#include <string>
using namespace std;

struct S
{
    string name;
    S ( string name ) : name ( name ) {}

    void operator + ( const S &other ) // member operator
    {
        cout << this->name << " . operator+ ( " << other.name << " )\n";
    }

    void m ( const S &other ) // member function
    {
        cout << this->name << " . m ( " << other.name << " )\n";
    }
};

void operator - ( const S &a, const S &b ) // external operator
{
    cout << "operator- ( " << a.name << ", " << b.name << " )\n";
}

void f ( const S &a, const S &b ) // external function
{
    cout << "f ( " << a.name << ", " << b.name << " )\n";
}

int main()
{
    S first ( "first" ), second ( "second" );

    first + second;
    first . operator+ ( second );
    first . m ( second );
    first - second;
    operator- ( first, second );
    f ( first, second );

    return 0;
}

output:

first . operator+ ( second )
first . operator+ ( second )
first . m ( second )
operator- ( first, second )
operator- ( first, second )
f ( first, second )

Think + as a function called 'operator+' which can be called using a syntax which differs from normal function calls

[ravpulp]

I can't thank you enough for you detailed explanation. Finally understand it!!! The speed and efficiency of you explanation is second to none!!!! Thanks again!!!