Editing Visitor pattern (section)

== Advantages ==
Moving operations into visitor classes is beneficial when
* many unrelated operations on an object structure are required,
* the classes that make up the object structure are known and not expected to change,
* new operations need to be added frequently,
* an algorithm involves several classes of the object structure, but it is desired to manage it in one single location,
* an algorithm needs to work across several independent class hierarchies.

A drawback to this pattern, however, is that it makes extensions to the class hierarchy more difficult, as new classes typically require a new <code>visit</code> method to be added to each visitor.