Duke CPS 1081. 1CPS 108, Fall 1999● Software Design and Implementation➤ Object oriented programming and design➤ good design helps do away with late night Teer-fests, but some late nights are inevitable➤ your toolkit must include mastery of language/programming and design● 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 idiomsDuke CPS 1081. 2Program Design and Implementation● Language independent principles of design and programming➤ design heuristics➤ coupling, cohesion, small functions, small interfaces ...➤ design patterns➤ factories, adapter, MVC aka observer/observable, ...● Language specific:➤ idioms➤ smart pointers, vectors/arrays, overloaded operators ...➤ idiosyncracies, idiocies➤ must define virtual destructor, stream zoo in Java, ...Duke CPS 1081. 3Administrivia● check website and news regularly➤ http://www.cs.duke.edu/courses/cps108/current/➤ duke.cs.cps108● 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➤ g++ 2.95, Java 2 aka 1.2Duke CPS 1081. 4C++ idioms/general concepts● templates➤ generic functions/container classes● inheritance➤ design guidelines, benefits, drawbacks● low-level structures➤ C-style arrays and strings compared to standard: STL, Tapestry● from C to C++➤ function pointers, function objects● build on generalities, transition to Java➤ vectors, interfaces, stress general principlesDuke CPS 1081. 5Design CriteriaGood 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➤ ?????Duke CPS 1081. 6How 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?specificationdesignimplementationDuke CPS 1081. 7Design 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 modificationDuke CPS 1081. 8Design patterns“... describes a problem which occurs over and over again in ourenvironment, and then describes the core of the solution to that problem, in such a way that you can use this solution a million times over, without ever doing it the same way twice”Christopher Alexander, quoted in GOF● Example: iterator➤ sequentially access elements of aggregate without exposing representation/implementation➤ see DirStream and other classes in libtapestry➤ heavily used in STL, with pointer like syntax● Factory➤ virtual constructor, have system that doesn’t depend on how items are createdDuke CPS 1081. 9Pattern Essentials● Name➤ good name provides a handle for the pattern, makes it easy to remember and use: vocabulary● Problem➤ when the pattern is applicable, context, criteria to be met, design goals● Solution➤ design, collaborations, responsibilities, and relationships of the classes/design elements● Consequences➤ trade-offs, problems, results from applying pattern: help in evaluating applicabilityDuke CPS 1081. 10larger group/company issuessee McCarthy, Dynamics of Software Development● establish a shared vision➤ what is hyperwag? what can we add?➤ harmonious sense of purpose● develop a creative environment➤ the more ideas the better, ideas are infectious➤ don’t flip the BOZO bit● scout the future➤ what’s coming, what’s the next project➤ what new technologies will affect this
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