Notes for Lecture 14 - March 6, 2007
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* Linear data structures
** Edit buffer ADT (text, chapter 9)
NewBuffer()
FreeBuffer()
MoveCursorForward()
MoveCursorBackward()
MoveCursorToStart()
MoveCursorToEnd()
InsertCharacter()
DeleteCharacter()
DisplayBuffer()

*** Array implementation
struct bufferCDT {
    char text[MaxBuffer];
    int length;
    int cursor;
};
**** Advantages
Cursor motion functions simple and constant time

**** Disadvantages
Insert and delete both Theta(n) operations
Has predetermined max size.  (Could overcome with datapack techniques.)

*** Two stack implementation
Consists of two stacks -- before and after.

**** Advantages
CursorForward, CursorBackward, InsertCharacter, DeleteCharacter constant time

**** Disadvantages
CursorToStart, CursorToEnd Theta(n)

*** Linked list with dummy header implementation
struct bufferCDT {
  cellT *start;
  cellT *cursor;
};

**** Dummy header cell
Convenient to have start point to a dummy cell, and dummy's next (link) 
pointer points to the chain of cells comprising the list.
Cursor points to the cell containing the character immediately to left of cursor.

**** Advantages
CursorForward, InsertCharacter, DeleteCharacter constant time

**** Disadvantages
CursorToEnd and CursorBackward both expensive.

*** Circular doubly linked list with dummy header implementation
Each cell has a next and a prev pointer.  Last element points to dummy.
Dummy's prev points to last element.

**** Advantages
All operations constant time (except freeing a list)

**** Disadvantages
More memory, more time for simple operations.


* Symbol table (a.k.a. dictionary)
Set of (key, value) pairs.
** ADT
*** symtab new_symtab() 
*** void free_symtab( symtab )
*** void insert( symtab table, char* key, void* value )
*** void* lookup( table, key )

** Demo 14.1_symtab


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