Functions with Default Arguments

1. C++ also allows one to introduce functions with default arguments.
   
   
2. In the function prototype, arguments having default values must appear after all the other arguments without default values, and their default values must be specified.
   
   
3. The function definition should be the same whether or not default arguments are used.
   
   
4. The function call may provide as few arguments as there are non-default arguments, up to the total number of parameter.
   
   
5. The arguments will be applied to the non-default arguments in order, then to the default arguments up to the total number of arguments.
   
   
6. //This program illustrates the use of a function with default arguments.
   
   #include <iostream>
   using namespace std;
   
   void drawLine(int len, char ch = '/', int nls = 1);
   // Draws a horizontal line of length len starting at the cursor
   // using the character ch, followed by nls newline characters.
   // The default character is '/'.
   // The default number of newline is 1.
   
   int main( )
   {
        // Must at least specify the number of character to print.
        // The 2 default arguments take on their default values.
        drawLine(50);
   
        // The second default argument take on its default value.
        drawLine(30,'#');
   
        // Want the second default argument to take on a non-default value.
        // The first default argument must then be specified
        // even though it take its default value.
        drawLine(50,'/',2);
   
        // Shows a line with nls = 0 (no newline)
        drawLine(30,'@',0);
   
        // The next line starts where the previous line ends.
        drawLine(20,'*');
   
        // A long line with nls = 5 (generating 4 blank lines).
        drawLine(79,'=',5);
   
        return 0;
   }
   
   void drawLine(int len, char ch , int nls)
   {
        for (int n = 1; n <= len; n++)
            cout << ch;
        for (n = 1; n <= nls; n++)
            cout << '\n';
   }