Design Pattern: Iterator (Behavioural) 1.0

Provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation [1]. This design pattern is also known as Cursor.Motivation: An example of an aggregate object is an instance of the List ADT. Consequently, an iterator can be used to traverse the elements of a list with a set of high-level abstract operations. These operations may be implemented within the List ADT but as Gamma et al.[1] wonderfully puts it, the key idea in this pattern is to take the responsibility for access and traversal out of the list object and put it into an iterator object - given the iterator describes behaviour whilst the list describes a collection.Implementation: The Iterator abstract class is used purely to specify the requirements of its concrete implementation. This abstraction could be implemented as an external/active or internal/passive iterator -External := the onus is on the client to advance the traversal and request next elements.Internal := the client can supply an operation to the iterator to perform over every element of a collectionRefer to pp.257-271 Gamma et al.[1] for more information on the Iterator (Behavioural) Design Pattern. Written by Bobby NedelkovskiMathWorks AustraliaCopyright 2009-2010, The MathWorks, Inc.Reference:[1] Gamma, E., Helm, R., Johnson, R. and Vlissides, J. Design Patterns : Elements of Reusable Object-Oriented Software. Boston: Addison-Wesley, 1995.

Requirements:	No special requirements
Platforms:	Matlab
Keyword:	Abstraction,  Advance,  Behavioural,  Client,  Collectionrefer,  Design,  Element,  Elementsinternal,  External,  Externalactive,  Implementation,  Information,  Internalpassive,  Operation,  Perform,  Pp257271,  Request,  Supply
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