Enhance the definition of the class StringVar given in Displays 11.11 and 11.12 by adding...

Enhance the definition of the class StringVar given in Displays 11.11 and 11.12 by adding al1 of the following:

■Member function copy_piece, which returns a specified substring; member function one_char, which returns a specified single character; and member function set_char, which changes a specified character

■An overloaded version of the == operator (note that only the string values have to be equal; the values of max_length need not be the same)

■An overloaded version of + that performs concatenation of strings of type StringVar

■An overloaded version of the extraction operator » that reads one word (as opposed to input_line, which reads a whole line)

If you did the section on overloading the assignment operator, then add it as well. Also write a suitable test program and thoroughly test your class definition