Editing Iterator (section)

{{short description|Object that enables processing collection items in order}}
{{More citations needed|date=June 2010}}In [[computer programming]], an '''iterator''' is an [[object (computing)|object]] that progressively provides access to each item of a [[Collection (abstract data type)|collection]], in order.<ref>{{cite web
 |url          = https://www.perl.com/pub/2005/06/16/iterators.html/
 |title        = Understanding and Using Iterators
 |last1        = Gatcomb
 |first1       = Joshua
 |publisher    = Perl.com
|date=Jun 16, 2005
 |quote        = A user-defined iterator usually takes the form of a code reference that, when executed, calculates the next item in a list and returns it. When the iterator reaches the end of the list, it returns an agreed-upon value.
 |access-date  = 2012-08-08
}}</ref><ref name=definition>{{cite web
 |url          = https://www.csd.uwo.ca/~watt/pub/reprints/2006-wgp-jflow.pdf
|date=September 16, 2006
 |title        = A Technique for Generic Iteration and Its Optimization
 |last1        = Watt
 |first1       = Stephen M.
 |publisher    = The University of Western Ontario, Department of Computer Science
 |quote        = Iterators were introduced as constructs to allow looping over abstract data structures without revealing their internal representation.
 |access-date  = 2012-08-08
}}</ref><ref>{{cite web
 | url        = http://www.cprogramming.com/tutorial/stl/iterators.html
 | title      = STL Iterators
 | author     = Alex Allain
 | publisher  = Cprogramming.com - Your resource for C and C++
 | quote      = You can think of an iterator as pointing to an item that is part of a larger container of items. 
 | access-date = 2012-08-08
}}</ref> 

A collection may provide multiple iterators via its [[Interface (object-oriented programming)|interface]] that provide items in different orders, such as forwards and backwards.

An iterator is often implemented in terms of the structure underlying a collection implementation and is often tightly [[Coupling (computer programming)|coupled]] to the collection to enable the operational semantics of the iterator.

An iterator is behaviorally similar to a [[cursor (databases)|database cursor]]. 

Iterators date to the [[CLU (programming language)|CLU]] programming language in 1974.