Simple Haskell Program

Write a Haskell program which will read a file named 'directory'(if it exists) and enable the user to add (a), remove (r), list (l) directory contents. List provides an index number (starting at 0) and the directory entry for each entry is in sorted order. In addition, when the user exits (x), the directory is saved in the file named 'directory'.

Each directory entry contains:
•firstName, lastName, telephoneNumber

From the terminal the user can enter:
•a firstName lastName telephoneNumber
•l
•r index
•x