Common Algorithmic Patterns

There are a great many popular design patterns. The list below includes a few of the most fundamental and popular patterns for implementing common operations.

Note that while these are described for object oriented languages, most of these patterns can be used in any language.
Remember, program into your language, not in it.

Object Abstraction Patterns

• Iterator
  A general interface to enumerating ordered lists, independently of their implementation.
• Visitor
  A means for causing client-supplied methods to be invoked on every element of a composite object ... making it possible to dynamically extend existing types with new methods.
• Command
  A means of representing operations as objects that can be instantiated, structured, enumerated and otherwise manipulated as data.
• Interpreter
  Creating a specialized language (typically very simple and with exactly the desired semantics) for expressing desired computations.

Flow Control Patterns

• Active Object
  Asynchronous invocation of object methods in schedulable parallel threads.
• Observer
  A Publish-Subscribe (pub/sub) event handling model where readers and writers exchange information without being aware of one-another. An observer registers a call-back function to be called when a specified event happens.
• Chain of Responsibility
  A command execution model, where a sequence of processing functions is given the opportunity to handle a request, until one of them claims and handles it. An easy way to support the dynamic addition of support for new (or sub-)commands.
• Pipes and Filters
  Constructing a desired transformation as a composition of a sequence of smaller (independent) transformations.

Concurrency Patterns

• Monitor
  A class-based approach to the serilialization of object method invocations.