Friend Functions - ordinary functions (i.e. non-member functions) that have extraordinary access to member variables

    syntax : prototype is in class definitiion
                prototype is preceded by keyword member

    using Friend functions vs using accessors

Example from Display 83. on page 447

void Money::input(istream& ins)
{
    char one_char, decimal_point, digit_1, digit_2;
    long dollars;
    int cents;
    bool negative;

    ins >> one_char;
    if (one_char == '-')
        {
        negative = true;
        ins >> one_char;
        }
    else
        negative = false;

    ins >> dollars >> decimal_point >> digit_1 >> digit_2;

    if (one_char != '$') || (decimal_point != '.') || !isdigit(digit_1) || !isdigit(digit_2))
        {
        cout << "Error - illegal form for money input\n";
        exit (1);
        }
 
    cents = digit_to_int(digit_1) *10 + digit_to_int(digit_2);

    all_cents = dollars * 100 + cents;
    if (negative)
        all_cents = -all_cents;
}

The helping function digit_to_int

    int digit_to_int(ch)
    {
       return int(ch) - int('0');
    }
 

Const Modifiers

    const parameters

    const member functions

Overloading Operators

Constructors for Automatic Type Conversion

Overloading Unary Operators

Overloading << and >>

Return to Comp 150 Home Page