Challenge #7

There is some starting code for a stringvar library here:-

Stringvar

Your task is to extend the code. First, take the time to make sure you understand how it works. Then add the following functions:-

* A member function called ‘one_char’, which returns a single specified character.
* A member function called ‘set_char’, which changes a single specified character.
* An overloaded version of the ‘==’ operator (only the values need be the same, max_length can be different).
* An overloaded version of the ‘+’ operator to allow stringvar concatenation
* A member function called ‘copy_piece’, which returns a specified substring.
* An overloaded version of the extraction operator ‘>>’, which reads in one word, while input_line reads in a whole line.