CS350: Data Structures Class Notes
Class 3: Friday, September 5, 2008
Announcements:
Shay Ellison will be tutoring in Olin 207 Sunday thru Thursday from 8:00 to 10:00PM.
Abstract Data Types Continued
Last time we did an intuitive introduction to ADT saying ADT’s have
• Specifications—what it does
• Implementations—how it does it
It is more correct to say the ADT is the specification and an ADT has an implementation.
Specifications include data and operations. We may need to define additional notation.
See the Shiflet example for an ADT for Integers.
Example: ADT for a LIST
Data: items on list
Operations (possible) include: create, destroy, empty?, size, first, rest, insert, delete, view
The first four (create, destroy, empty?, & size) are very common for aggregate data
structures. Some (e.g., insert, delete, view) can take a position in the list as an argument,
can default to the first item in the list, or can have an implied position (See Shiflet
example distributed in class for the latter.)
Notice that some operations can be defined in terms of others. E.g.,
list.view() could be written as
x = list.remove()
list = list.insert(x)
return x
Consider LISP/SCHEME with NIL, CAR, CDR, CONS, EMPTY? These are enough to
define the List type (along with implicit operations such as garbage collection.
Obviously, we have a lot of choices on what function to include in an ADT
