Exercises

1. Construct (by hand) the letter tree for cat, cake, cook, coat and assert it into the database.
2. Write a program which adds a word to a letter tree
3. Implement find_word as shown above and test it on the tree you just asserted.
4. Modify find_word so that a word can have more than one lexical entry, e.g.

   [c,[a,[n,verb(can),noun(can)]]]

5. Improve the efficiency of find_word by exploiting lexicographic ordering