are some sites recommended by Jim Coplien, of C++ fame (http://www.bell-labs.com/~cope), who is one of the main proponents of the patterns movement:

http://st-www.cs.uiuc.edu/users/patterns http://c2.com/cgi/wiki http://c2.com/ppr

http://www.bell-labs.com/people/cope/Patterns/Process/index.html http://www.bell-labs.com/cgi-user/OrgPatterns/OrgPatterns http://st-www.cs.uiuc.edu/cgi-bin/wikic/wikic http://www.cs.wustl.edu/~schmidt/patterns.html http://www.espinc.com/patterns/overview.html

Also note there has been a yearly conference on design patterns, called PLOP, that produces a published proceedings. The third one of these proceedings came out in late 1997 (all published by Addison-Wesley).

Exercises

1.Using SingletonPattern.cpp as a starting point, create a class that manages a fixed number of its own objects. Assume the objects are database connections and you only have a license to use a fixed quantity of these at any one time.

2.Create a minimal Observer-Observable design in two classes, without base classes and without the extra arguments in Observer.h and the member functions in Observable.h. Just create the bare minimum in the two classes, then demonstrate your design by creating one Observable and many

Observers, and cause the Observable to update the Observers.

3.Change InnerClassIdiom.cpp so that Outer uses multiple inheritance instead of the inner class idiom.

4.Add a class Plastic to TrashVisitor.cpp.

5.Add a class Plastic to DynaTrash.cpp.

6.Explain how AbstractFactory.cpp demonstrates Double Dispatching and the Factory Method.

7.Modify ShapeFactory2.cpp so that it uses an Abstract Factory to create different sets of shapes (for example, one particular type of factory object creates “thick shapes,” another creates “thin shapes,” but each factory object can create all the shapes: circles, squares, triangles etc.).

8.Create a business-modeling environment with three types of Inhabitant: Dwarf (for engineers), Elf (for marketers) and Troll (for managers). Now create a class called Project that creates the different inhabitants and causes them to interact( ) with each other using multiple dispatching.

9.Modify the above example to make the interactions more detailed. Each

Inhabitant can randomly produce a Weapon using getWeapon( ): a Dwarf uses Jargon or Play, an Elf uses InventFeature or

SellImaginaryProduct, and a Troll uses Edict and Schedule. You must decide which weapons “win” and “lose” in each interaction (as in

PaperScissorsRock.cpp). Add a battle( ) member function to Project that takes two Inhabitants and matches them against each other. Now create a meeting( ) member function for Project that creates groups of Dwarf, Elf and Manager and battles the groups against each other until only members of one group are left standing. These are the “winners.”

10.Implement Chain of Responsibility to create an “expert system” that solves problems by successively trying one solution after another until one matches. You should be able to dynamically add solutions to the expert system. The test for solution should just be a string match, but when a solution fits, the expert system should return the appropriate type of problemSolver object. What other pattern/patterns show up here?