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Stategy and Composite - Using C++ Templates for Implementation of Patterns

Stategy and Composite - Using C++ Templates for Implementation of Patterns  
 
 
ABSTRACT
 
 
Originally, templates were introduced to the language in order to express common structure in form of parameterized types implemented as class templates. Function templates, in addition, allow expression of common functionality. Using the template language feature in C++, several patterns as defined by Gamma et.al. can be implemented using templates instead of inheritance and virtual functions. Often, classic object oriented runtime polymorphism can be replaced by a compile time polymorphism, the effect of which is a considerable gain in runtime performance. 

The template technique leaves behind classic object oriented approaches, and for that reason many C++ programmers do not even consider it as an alternative. Yet it has been widely used in areas of C++ programming, where performance is crucial: 

  • Foundation libraries such as the Booch components and the STL prove that the template version of strategy and other patterns are of great value in practice.
  • Expression templates, based on the idea of the interpreter pattern, speed up scientific computating considerably, as the Blitz++ library demonstrates. 
In this tutorial, the alternative template technique is demonstrated using the strategy pattern and the composite and interpreter patterns as examples. The intent is to expand the attendants' set of programming techniques by another useful mechanism based on template programming. Naturally, the decision between runtime techniques on the one hand and compile time mechanisms on the other hand cannot be made without a sound knowledge of the respective trade-offs. Hence, we will carefully evaluate the respective advantages and drawbacks.
 
 
PREREQUISITES

 
 
Level: intermediate
Duration: 2 - 3 hours
Prerequisites: Attendants should be familiar with the concept of C++ templates.  Any knowledge of patterns is not required.
Presented at: C++ World '99 , Miami, FL, December 1999 
DevWeek Europe 2000 , London, UK, February 2000 
Zühlke Forum , Zürich, CH, March 2000 
TOOLS USA 2000 , Santa Barbara, CA, August 2000 
OOPSLA 2000 , Minneapolis, MN, October 2000 
ROOTS 2001 , Bergen, Norway, May 2001

 
 

If you are interested to hear more about this and related topics you might want to check out the following seminar or skim through some further reading:
Seminars
 
Compile Time Computations in C++ -
Programming with Templates
3-day seminar (open enrollment and on-site)
 
Paper
 
Compile Time Computations in C++ -
Novel Template Programming Techniques
short white paper (providing first insights)
C++ Expression Templates
article published in C/C++ Users Journal
 
  © Copyright 1995-2012 by Angelika Langer.  All Rights Reserved.    URL: < http://www.AngelikaLanger.com/Conferences/Abstracts/PatternsAndTemplates.htm  last update: 3 Nov 2012