Editing Composite pattern (section)

== Motivation ==
When dealing with Tree-structured data, programmers often have to discriminate between a leaf-node and a branch. This makes code more complex, and therefore, more error prone. The solution is an interface that allows treating complex and primitive objects uniformly. In [[object-oriented programming]], a composite is an object designed as a composition of one-or-more similar objects, all exhibiting similar functionality. This is known as a "[[has-a]]" relationship between objects.<ref>{{cite book|url=http://perldesignpatterns.com/?CompositePattern|title=Perl Design Patterns Book|author=Scott Walters|year=2004|access-date=2010-01-18|archive-url=https://web.archive.org/web/20160308182256/http://perldesignpatterns.com/?CompositePattern|archive-date=2016-03-08|url-status=dead}}</ref> The key concept is that you can manipulate a single instance of the object just as you would manipulate a group of them. The operations you can perform on all the composite objects often have a [[least common denominator]] relationship. For example, if defining a system to portray grouped shapes on a screen, it would be useful to define resizing a group of shapes to have the same effect (in some sense) as resizing a single shape.