Abstract Data Types

• From the Dictionary
  
  Abstract -- a concept, thought, or idea apart from any particular instances or material objects.
  
  Abstraction -- formation of an idea, such as the qualities or properties of a thing, separate from any particular instances of a thing or material objects.
  
  
• In Computer Science
  
  Abstract -- an organization of data, a manipulation of data, an algorithm etc. apart from any particular programming language implementation of that thing.
  
  Abstraction -- A model of a complex system that includes only the details essential to the perspective of the viewer of the system.
  
  
• Abstract Data Type -- A data type whose properties (domain and operations) are specified independently of any particular implementation. Examples covered in class: List, Stack, Queue, Tree, Graph, and Set.

• Data Abstraction -- The separation of a data type's logical properties from its implementation.
  
  
• Data Encapsulation -– (Another term for Data Abstraction) The separation of the representation of data from the applications that use the data at a logical level; a programming language feature that enforces information hiding.
  
  
• Information Hiding -– The practice of hiding the details of a function or data structure with the goal of controlling access to the details of a module or structure.
  
  
• Domain -- the set or range of data that an abstract data type acts on. Example: the domain of the int data type is all whole numbers. In a computer it is the range of whole numbers that can be represented by the operating system's implementation of the int data type.
  
  
• Operations -- All the functions that act on the data. Example: for the int data type these operations include +, -, *, /, %, &, |, etc.
  
  

Categories of Operations

1. Constructors - Functions that create an abstract data type. Example: int x; or new node(); Also the constructor function in a C++ class.
2. Transformers (mutators) - Functions that change the data in some way. Example: x = 3; The equals function sets the value store in the variable x. This may include setting values, inserting or deleting an item from an object, combining two objects (binary transformer -- example x = 2 + 3; plus (+) is the binary transformer insert() or delete() in an ADT change the data stored.
3. Observers - Functions that allow us to observe the state of one or more of the data values
   1. Predicates -- asks if a certain property is true, example: isEmpty();
   2. Accessor or selector -- returns a copy of a data object, example: getX();
   3. Summary -- return information about the object as a whole, example: getListLength();
4. Iterators - Functions that perform some sequential action on all data components in an object. Example: setAll(value);