HOMEWORK PROBLEM 10           INTRODUCTION TO Ada 95

  PURPOSE:      To learn about access types
                Binary trees are used because they rather naturally
                dictate the use of access types.

  END RESULT:   A complete Ada program that is a main procedure
                that WITH's a package containing the binary tree
                manipulation routines INSERT, FIND, DELETE and OUTPUT.
                Use OUTPUT as a debugging aid as each feature is added.

  PROBLEM:      Use the attached samples as a guide to write a package
                that has binary tree manipulation routines. You must
                add a procedure DELETE that takes a name and deletes
                the names node from the tree. You can build the same
                tree. To show that the cases work delete ( in order )
                "E " , "B " , and "D " . Make provision for doing
                nothing to the tree if the name is not in the tree.
                Output the tree after every delete.

  TURN IN:      Printout main procedure and package.
                Printout of execution for built in test data.

  OBSERVE:      These tree manipulation routines are messy if recursive
                procedures and functions are not used. These happen
                to be in the class of "simple" recursive routines that
                can be thoroughly tested to be sure they terminate.

  READING :     ISO 8652:1995  3.10 plus
                use the index for all references to "access"
                Barnes   10.1, 10.2, 10.4

  EXTRA :       For extra credit make the INSERT and DELETE work
                to maintain a balanced binary tree. This uses the
                balance factor  BF. The INSERT is not too difficult
                but the DELETE is a bear! It turns out that just plain
                binary trees are very inefficient. But, balanced binary
                trees are very efficient. If the tree is maintained
                in balanced form at most  O(log2 N) searches are needed
                for an INSERT, FIND or DELETE. On a Baltimore phone
                book N is a large number! An unbalanced tree could be
                the worse possible structure if the names were entered
                alphabetically. Zzepth could be all day looking for his
                phone number.

  FILES:        The starter file is hw10.ada and for gnat hw10.bat.
                The file can be obtained by ftp from 
                sigpro.md.essd.northgrum.com/pub/ada95 or
                from ECLUS::DISK2[ADA.ADA95} or on disk from instructor