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Topic: Iterator pattern

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	Iterator Pattern
		If the iterator is defined in the class itself, then it is easier to ensure that any changes to the class are reflected in the iterator.
		For most iterators one comes in both flavors, pre-increment and post-increment and unlike normal loops that use simple types for positioning iterators should be advanved with the pre-increment operator to avoid creating a copy of the iterator.
		Iterator creation is typically done by calling a begin() method and the end of iteration can be detected by comparing the iterator to the element behind the elements, typically there is a method end().
	c2.com /cgi/wiki?IteratorPattern (704 words)

	Patterns for PHP: Iterator - Jacob Santos - Web and Game Development (Site not responding. Last check: )
		The Iterator pattern is not constrain to the class for which holds the data.
		The iteration in classes is not as simple as collecting all of the data and passing it off to the developer.
		The method for which to control iteration is to either pass SQL to the iterator or to pass the mysql_query() resource to the iterator.
	www.santosj.name /php/patterns-for-php-iterator (1331 words)

	[No title]
		An iterator object is responsible for keeping track of the current element; that is, it knows which elements have been traversed already.
		Consider a typical iterator application: given binary tree, define one iterator to traverse it in inorder, another to traverse the same tree in preorder, yet another in reverse inorder, and so so on.
		Iterator examples ================= Consider the situation where a client class needs a sequence of numbers, but wants to be independent whether that sequence is stored in an array, a linked list, a tree, or is computed on the fly by an algorithm, and so on.
	csr.uvic.ca /~vanemden/oosd/2.patt/05.iteratorPatt.txt (1117 words)

	SENG 609.04 Design Patterns: Iterator Pattern in Java 1.2
		The Iterator pattern, as defined by Gamma et al., "Provides a way to access the elements of an aggregate object sequentially without exposing its underlying representation." (Gamma, 1995, pg 257) The developers of the Java language have included an implementation of Iterator as a defined interface in the collections framework of JDK 1.2.
		This paper presents a brief overview of the Iterator pattern, the Iterator interface in Java and it's relation to the iterator design pattern, and the role of the Iterator interface in the Collections framework of JDK 1.2.
		The Iterator interface is intended to be used with any type of collection, but, in the interest of brevity and without any real loss of generality, the rest of this paper will only discuss the use of the ListIterator interface, as that is a more obvious implementation of the Iterator design pattern.
	sern.ucalgary.ca /courses/SENG/609.04/W98/jonesb/iterator.html (2671 words)

	Design Pattern Synopses
		The Filter pattern is a special case of the Decorator pattern, where a data source or data sink object is wrapped to add logic to the handling of a data stream.
		The Composite pattern also allows the objects in the tree to be manipulated in a consistent manner, by requiring all of the objects in the tree to have a common superclass or interface.
		The Flyweight pattern is often combined with the Composite pattern to represent the leaf nodes of a hierarchical structure with shared objects.
	www.mindspring.com /~mgrand/pattern_synopses.htm (4381 words)

	Iterator
		The Iterator abstraction is fundamental to an emerging technology called "generic programming".
		In office settings where access to files is made through administrative or secretarial staff, the Iterator pattern is demonstrated with the secretary acting as the Iterator.
		Memento is often used in conjunction with Iterator.
	home.earthlink.net /~huston2/dp/iterator.html (831 words)

	Object Oriented Design and Programming - Software Design Principles and Design Patterns - Iterator Pattern
		The idea of the iterator pattern is to take the responsibility of accessing and passing trough the objects of the collection and put it in the iterator object.
		The iterator should be aware of the new size of the collection and to iterate till the end.
		In this case the operation to change the iteration should be added to the iterator interface or base class not to the implementation only, in order to have a general mechanism for the entire application.
	www.oodesign.com /iterator-pattern.html (1305 words)

	Iterator Pattern (Site not responding. Last check: )
		The iterator pattern shifts responsibility for traversal out of the aggregate object and into an iterator class.
		The iterator object is responsible for keeping track of the current element in the traversal.
		Composite iterators may be difficult to implement, because iterator must maintain path through a complex structure.
	web.cs.wpi.edu /~gpollice/cs509-s04/Patterns/IteratorPattern.html (315 words)

	Iterator pattern - Wikipedia, the free encyclopedia
		In object-oriented programming, the Iterator pattern is a design pattern in which iterators are used to access the elements of an aggregate object sequentially without exposing its underlying representation.
		An Iterator object encapsulates the internal structure of how the iteration occurs.
		Multiple Iterator classes are available with PHP to allow you to iterate through common lists, such as directories, XML structures and recursive arrays.
	en.wikipedia.org /wiki/Iterator_pattern (325 words)

	Application Development Trends - A tale of three patterns
		Iteration can be supported directly in the collection by providing the collection with the notion of a current position.
		The methods of the collection cannot use the iteration mechanism for fear they may upset an existing iteration; a collection may be referenced by many objects, each with its own use for the notion of a "current position," and there is therefore a strong possibility of interference between them.
		The separation of iteration from the interface of the collection means that collection users can customize their own iteration by adapting the raw iterator, i.e., defining a search iterator that skips elements that do not match some particular condition when it traverses.
	www.adtmag.com /java/article.aspx?id=4859 (2627 words)

	CIOL IT Unlimited (Site not responding. Last check: )
		Iterator is one of the most widely used GOF Design Patterns and one of the patterns included in JDK Core API.
		The traversal algorithm when kept in iterators, its easy to reuse them, on the other hand the algorithms may need to access some private variables of the aggregate which violates the encapsulation of the aggregate.
		There are some differences between this interface and the Iterator in the iterator design pattern, most notably the addition of a remove method, and the exclusion of the CurrentItem(), and First() methods.
	www.ciol.com /content/search/showarticle.asp?artid=27460 (819 words)

	Iterator
		Internal iterators are easier to use, because they define the iteration logic for you.
		They require the iterator object to be allocated dynamically by a factory method, not on stack.
		External iterators can be difficult to implement over recursive aggregate structures, since it has to store a path through the Composite to keep track of the current object.
	www.cs.unb.ca /profs/wdu/cs4015w02/ch5d.htm (1182 words)

	Patterns
		The BluePrints patterns catalog is based around the Sun Java Center patterns catalog, described in the Core J2EE Patterns book by Deepak Alur, John Crupi, and Dan Malks.
		Patterns reflect the experience, knowledge and insights of developers who have successfully used these patterns in their own work.
		A pattern description indicates when the pattern may be applicable, but only experience can provide understanding of when a particular pattern will improve a design.
	java.sun.com /blueprints/patterns/index.html (395 words)

	design:the_iterator_pattern [phpPatterns]
		Using an Iterator pattern, we can unify all these these situations to provide a single API so that stepping through a set of database results can be done in exactly the same way as stepping through the contents of a file (or an array containing an XML-RPC response...).
		In general the Iterator pattern is intended to provide a simple API for moving through “collections”.
		In general the way an Iterator is normally implemented is to accept the container as an argument in the Iterator’s constructor (or provide a method for adding containers) then provide an API much like the one above (e.g.
	www.phppatterns.com /docs/design/the_iterator_pattern (2221 words)

	O'Reilly Network -- What Is an Iterator in C++, Part 1
		An iterator in C++ is a concept that refines the iterator design pattern into a specific set of behaviors that work well with the C++ standard library.
		The iterator pattern describes a set of requirements that allows a consumer of some data structure to access elements in it with a familiar interface, regardless of the internal details of the data structure.
		The concept of an iterator is something that allows two parties--generally the consumer of some data structure or "client code", and the implementer of the data structure, or "library code"--to communicate without concern for the other's internal details.
	www.oreillynet.com /pub/a/network/2005/10/18/what-is-iterator-in-c-plus-plus.html (782 words)

	Enterprise .NET Community: Iterators With C#2
		C#2 iterator is also a good mean to implement concisely several iterators on a single enumerable.
		Iterators are perfect to implement the pipeline pattern, the one that you have used so many times in your shell windows.
		The limitation of C#2 iterators that is pinpointed here is the impossibility for an iterator object to reference and call itself.
	www.theserverside.net /articles/showarticle.tss?id=IteratorsWithC2 (2908 words)

	Iterator Design Pattern
		The intent of this design pattern is to provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation.
		The idea of this pattern is to take the responsibility for access and manipulation of the data structure out of the list object and put it into the iterator object.
		Iterator Pattern supports variations in the traversal of an aggregate.
	www.cs.uofs.edu /~bi/2003f-html/se516/iterator.htm (432 words)

	SENG 609.04
		The intention of the iterator pattern is to "provide a way to access the elements of an aggregate object sequentially without exposing its underlying representation" (Gamma, 1995).
		Separate iterators for different traversal polices can be defined in the Iterator pattern without enumerating them in the List interface and Iterator can also be generalized to support polymorphic iteration.
		The iterator pattern can be used to support multiple traversals of aggregate object and accessing an aggregate object's components without exposing its internal representation.
	www.ucalgary.ca /~samulee/seng60904/iterator.html (461 words)

	Iterator Pattern Files : Forest and the Trees
		Iterating on an interval without having to add much to your main class.
		Because your iterator class is external to the class that is calling the iteration, the class that calls the iteration is able to treat a hash identically to an array.
		For internal iterations, you pass a method to the class that holds the data, the data class traverses over its data and modifies the data using the method passed.
	www.forestandthetrees.com /?p=81 (358 words)

	Iterator Pattern
		Il pattern Iterator fornisce una soluzione per implementare una o più di queste caratteristiche.
		Chi ha studiato il Factory Method Pattern già immaginerà la soluzione: un metodo (factory method per l'appunto) che costruisce l'oggetto iterator a livello di superclasse, in modo da avere due gerarchie parallele.
		Composite iterators: implementare un iterator esterno per una struttura Composite (che è in sostanza una composizione ricorsiva) può essere complesso, in quanto è necessario mantenere traccia del percorso necessario a raggiungere l'oggetto.
	www.ugolandini.net /IteratorPattern.html (1021 words)

	perl.com: Perl Design Patterns (Site not responding. Last check: )
		In 1995, Design Patterns was published, and during the intervening years, it has had a great influence on how many developers write software.
		Essential patterns are integrated into the core of the language.
		So the iterator pattern from GoF is a core part of Perl we hardly think about.
	www.perl.com /pub/a/2003/06/13/design1.html (2058 words)

	XML.com: Design Patterns in XML Applications
		Patterns are not miraculous recipes that will work in every scenario, but they do convey important knowledge, a standard solution, and a common language about a recurrent problem.
		Wrapper is a structural pattern used to allow an existing piece of software to interact in an environment different from its originally intended one.
		The difference between the patterns is not predominantly structural, but rather in their intentions: Adapter seeks to make an existing object work with other known objects that expect something, while Wrapper is focused on providing a different interface (without knowing in advance its clients) and solving platform/language issues.
	www.xml.com /lpt/a/2000/01/19/feature/index.html (2843 words)

	SENG 609.04
		The Proxy pattern is a structural pattern that has the intent to "provide a surrogate or placeholder for another object to control access to it." In other words, at allows for a proxy object to act as a stand-in for the real object.
		As an example for the latter, this pattern is the basis for the Java RMI protocol.
		The Abstract Factory is a creational pattern that has the intent to "provide an interface for creating families of related objects or dependant objects without specifying their concrete classes." Thus, the type of an individual object that is to be created is decoupled from the act of creation.
	pages.cpsc.ucalgary.ca /~laf/609.04/week3.html (681 words)

	Java Tip 38: The trick to "Iterator Observers" - Java World (Site not responding. Last check: )
		Readers familiar with these two patterns may want to move straight to the section called Iterator Observers.
		Iterators provide an abstract mechanism to access elements in collection classes without revealing their underlying representations.
		Those readers who are interested in experimenting with Iterators should write a class that can read a row at a time from a text file, or even better from a database table, and provides an iterator over the rows in the form of the
	www.javaworld.com /javaworld/javatips/jw-javatip38.html (505 words)

	Five more PHP design patterns
		Before adding an iterator pattern, if you're looping through the person's addresses, you might loop through the physical addresses and display them, then loop through the person's e-mail addresses and display them, then loop through the person's IM addresses and display those.
		An iterator is powerful because you can add new types of items through which to iterate, and you don't have to change the code that loops through the items.
		The state pattern is a similar to the command pattern, but the intent is quite different.
	www.ibm.com /developerworks/opensource/library/os-php-designpatterns (2325 words)

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