CPS 108, Spring 2004Application Programming Interface, APIProgram Design and ImplementationAdministriviawordlines.cpp, understanding codeQuestions about wordlines.cppClasses: Review/OverviewC++ (and Java) class constructionDesign CriteriaHow to codeXP and RefactoringModules, design, coding, refactor, XPDesign Heuristics: class/program/functionC++ idioms/general conceptsStandard LibrariesEric RaymondSoftware Design1.1CPS 108, Spring 2004Software Design and ImplementationObject oriented programming and design•Language independent concepts including design patterns, e.g., Model-View-Controller, iterator, factory, bridge, …•Design independent concepts, e.g., coupling, cohesion, testing, refactoring, profiling, …What’s in the course?C++ and Java, team projects, mastery exams•team projects can be more and less than the sum of their partshigh-level abstractions, low-level details•patterns, heuristics, and idiomsSoftware Design1.2Application Programming Interface, APIStandard C++ headers, STL headersCurseswxWindowsJava APIjava.util, javax.swing, java.net, javax.crypto, …Eclipse SWTGoogle APIGracenote APISoftware Design1.3Program Design and ImplementationLanguage independent principles of design and programmingdesign heuristics•coupling, cohesion, small functions, small interfaces ...design patterns•factories, adapter, MVC, decorator, iterator, …Language specific:Idioms•smart pointers, vectors/arrays, overloaded operators ...idiosyncracies, idiocies•must define virtual destructor, stream zoo in Java, ...Software Design1.4Administriviacheck website and bulletin board regularlyhttp://www.cs.duke.edu/courses/cps108/current/See links to bulletin board and other stufGrading (see web pages)group projects: small, medium, largemastery programs (solo or semi-solo endeavors)readings and summariestestsEvaluating team projects, role of TA, UTA, consultantsface-to-face evaluation, early feedbackCompiling, tools, environments, Linux, Windows, Macg++ 3.3, Java 2 aka 1.4, JRE, …Software Design1.5wordlines.cpp, understanding code typedef map<string, set<int> > linemap; while (getline(input,line)) { linecount++; istringstream iline(line); while (iline >> w) { linemap::iterator it = info.find(w); if (it == info.end()) { set<int> si; si.insert(linecount); info.insert(make_pair(w,si)); } else { it->second.insert(linecount); } } }Software Design1.6Questions about wordlines.cppConceptually, what's a map and what's a set?In terms of implementation how do they work?What's an iterator (abstractly and concretely)What are streams? ifstream, cin/cout, istring/ostring, …What's a templated class?Other questions?Software Design1.7Classes: Review/OverviewA class encapsulates state and behaviorBehavior first when designing a classInformation hiding: who knows state/behavior?State is private/protected; some behavior is publicPrivate/protected helper functionsA class is called an object factory, creates lots of instancesClasses communicate and collaborateParameters: send and receiveContainment: has a reference toInheritance: is-aSoftware Design1.8C++ (and Java) class constructionC++ uses .h and .cpp, Java uses .javaDocumentation diferent (javadoc vs. ???)Default ctor, copy constructor, destructor, assignment operatortvector, string, DateCopy constructor needed to avoid shallow copyIn C++ destructors needed to free resources/self, Java?Clone makes copy in Java (rare), share is default Private, protected, public, (package)Private default in C++, package default in JavaPer method declaration in Java, class sections in C++Software Design1.9Design Criteria Good design comes from experience, experience comes from bad designFred Brooks (or Henry Petroski)Design with goals:ease of useportabilityease of re-useefficiencyfirst to market?????Software Design1.10How to codeCoding/Implementation goals:Make it runMake it rightMake it fastMake it smallspiral design (or RAD or !waterfall or ...)what’s the design methodology?specificationdesignimplementationSoftware Design1.11XP and Refactoring(See books by Kent Beck (XP) and Martin Fowler (refactoring))eXtreme Programming (XP) is an agile design processCommunication: unit tests, pair programming, estimationSimplicity: what is the simplest approach that works?Feedback: system and clients; programs and storiesCourage: throw code away, dare to be great/diferentRefactoringChange internal structure without changing observable behaviorDon’t worry (too much) about upfront designSimplicity over flexibility (see XP)Software Design1.12Modules, design, coding, refactor, XPMake it run, make it right, make it fast, make it smallDo the simplest thing that can possibly work (XP)Design so that refactoring is possibleDon’t lose sight of where you’re going, keep change in mind, but not as the driving force [it will evolve]Refactor: functionality doesn’t change, code doesShould mean that new tests aren’t written, just re-runDepends on modularity of code, testing in piecesWhat’s a module in C++Could be a class, a file, a directory, a library, a namespaceWe should, at least, use classes, files, directoriesSoftware Design1.13Design Heuristics: class/program/function(see text by Arthur Riel)Couplingclasses/modules are independent of each othergoal: minimal, loose couplingdo classes collaborate and/or communicate?Cohesionclasses/modules capture one abstraction/modelkeep things as simple as possible, but no simplergoal: strong cohesion (avoid kitchen sink)The open/closed principleclasses/programs: open to extensibility, closed to modificationSoftware Design1.14C++ idioms/general conceptsGenericityTemplates, STL, containers, algorithmsCopy/Assignment/MemoryDeep copy model, memory management “required”Low-level structuresC-style arrays and strings compared to STL, TapestryconstGood for clients, bad for designers/coders?From C to C++ to Javafunction pointers, function objects, inheritanceSoftware Design1.15Standard LibrariesIn C++ there is the Standard Library, formerly known as the Standard Template Library or STLEmphasizes generic programming (using templates)Write a sorting routine, the