String Encryption Write a class EncryptableString that is derived from the STL string class. The Encryptable string class adds a member function void encrypt( ) That encrypts the string contained in...

String Encryption

Write a class EncryptableString that is derived from the STL string class. The

Encryptable string class adds a member function

void encrypt( )

That encrypts the string contained in the object by replacing each letter with its successor

in the ASCII ordering. For example, the string baa would be encrypted to cbb. Assume that

all characters that are part of an EncryptableString object are letters a, .., z and A, .., Z,

and that the successor of z is a and the successor of Z is A. Test your class with a program

that asks the user to enter strings that are then encrypted and printed.