// overload ostream insertion operator<< friend ostream &operator<< (ostream &stm, Frac const &rhs) { stm << rhs.num << “/” << rhs.den; }

// overload ostream insertion operator<< friend ostream &operator<< (ostream &stm, Frac const &rhs) { stm << rhs.num << “/” << rhs.den; }

Overloading the Stream Insertion Operator (<<)

To enable seamless integration of custom data types with C++’s standard output streams, such as std::cout, the stream insertion operator (<<) must be overloaded. For a class Frac representing a fraction, this allows an object of the class to be printed in an intuitive and readable format, just like a built-in type.

The standard approach is to implement this overload as a non-member function. Since the function needs to access the private members of the Frac class (specifically, num and den), it is declared as a friend inside the class definition.

class Frac {
    int num, den;
public:
    // ... other members and constructors ...

    // Friend declaration for the stream insertion operator
    friend std::ostream& operator<<(std::ostream& stm, Frac const& rhs);
};

// Function implementation
std::ostream& operator<<(std::ostream& stm, Frac const& rhs) {
    stm << rhs.num << "/" << rhs.den;
    return stm;
}

content_copydownloadUse code with caution.C++

Explanation

This implementation follows a standard, robust pattern for operator overloading. Let’s break down the function signature: std::ostream& operator<<(std::ostream& stm, Frac const& rhs).

1. Return Type (std::ostream&): The function returns a reference to an ostream object. This is crucial for enabling chaining of output operations. For instance, in the statement std::cout << f1 << ” and ” << f2;, the expression std::cout << f1 is evaluated first. It calls the overloaded operator, which prints the fraction and then returns the std::cout stream itself. This returned stream then becomes the left-hand operand for the next << operator, allowing the chain to continue.
2. Function Name (operator<<): This is the special name C++ uses to signify an overload of the << operator.
3. First Parameter (std::ostream& stm): This is a reference to the output stream that the object is being sent to (e.g., std::cout). It is passed as a non-const reference because the act of writing to the stream modifies its internal state.
4. Second Parameter (Frac const& rhs): This is the object to be printed—the right-hand side of the << operator. It is passed as a constant reference (const&) for two key reasons: efficiency (avoiding a costly copy of the object) and safety (guaranteeing that the print operation does not modify the object).

The function body simply sends the numerator, a slash character, and the denominator to the stream stm. Finally, returning stm ensures the operator can be used in chained expressions.thumb_upthumb_down