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Fix Acyclic Visitor readme layout

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Ilkka Seppälä 2019-12-13 09:36:57 +02:00
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acyclic-visitor/README.md
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@ -17,6 +17,7 @@ Allow new functions to be added to existing class hierarchies without affecting
## Applicability
This pattern can be used:
* When you need to add a new function to an existing hierarchy without the need to alter or affect that hierarchy.
* When there are functions that operate upon a hierarchy, but which do not belong in the hierarchy itself. e.g. the ConfigureForDOS / ConfigureForUnix / ConfigureForX issue.
* When you need to perform very different operations on an object depending upon its type.
@ -25,11 +26,13 @@ This pattern can be used:
## Consequences
The good:
* No dependency cycles between class hierarchies.
* No need to recompile all the visitors if a new one is added.
* Does not cause compilation failure in existing visitors if class hierarchy has a new member.
The bad:
* Violates the principle of least surprise or Liskov's Substitution principle by showing that it can accept all visitors but actually only being interested in particular visitors.
* Parallel hierarchy of visitors has to be created for all members in visitable class hierarchy.