Nifty Assignments:Nifty Assignments:Marine Biology SimulationMarine Biology Simulation

OOPSLA ‘04 Educators’ SymposiumOOPSLA ‘04 Educators’ Symposium

October 25, 2004October 25, 2004

Eric ChengEric Cheng

Mathias RickenMathias Ricken

Dung “Zung” NguyenDung “Zung” Nguyen

Stephen WongStephen Wong

Marine Biology SimulationMarine Biology Simulation

Based on AP Marine Biology SimulationBased on AP Marine Biology SimulationCompletely redone using OO designCompletely redone using OO design

More robust, flexible, and extensibleMore robust, flexible, and extensible

Two-week assignment in our objects-first Two-week assignment in our objects-first CS2 coursesCS2 courses

Requires broad range of skillsRequires broad range of skills

Assignment and Source Code AvailableAssignment and Source Code Availablehttp://www.owlnet.rice.edu/~comp202http://www.owlnet.rice.edu/~comp202

Marine Biology SimulationMarine Biology Simulation

DemoDemo

Structure of the AssignmentStructure of the Assignment

Milestone 1Milestone 1Part 1: KnightFishPart 1: KnightFish

Add a new fish species to the simulationAdd a new fish species to the simulation

Part 2: WrappingEnvPart 2: WrappingEnv

Add a new kind of environmentAdd a new kind of environment

Milestone 2Milestone 2Part 3: InternalsPart 3: Internals

Re-implement parts of the simulation frameworkRe-implement parts of the simulation framework

Part 4: Behavior StrategiesPart 4: Behavior Strategies

Refactor framework to allow dynamic behavior changesRefactor framework to allow dynamic behavior changes

Support code includes

solution to Milestone 1

Part 1: KnightFishPart 1: KnightFish

Randomly pick Randomly pick one of 8 targetsone of 8 targets

11 22

33

44

5566

77

88

Part 1: KnightFishPart 1: KnightFish

Turn into right Turn into right directiondirection

For each stepFor each stepIf blocked, doneIf blocked, done

If open, go there If open, go there and attempt the and attempt the next stepnext step

33

Part 1: KnightFishPart 1: KnightFish

Complicated behaviorComplicated behaviorProcedural programming: nested if-statementsProcedural programming: nested if-statements

OOP: nested visitorsOOP: nested visitors

Visitor-Based Delegation ModelVisitor-Based Delegation ModelProcess flow diagramming Process flow diagramming makes designing makes designing complex algorithms a systematic processcomplex algorithms a systematic process

Cannot forget to handle a situation (compiler Cannot forget to handle a situation (compiler error!)error!)

Part 2: WrappingEnvPart 2: WrappingEnv

Grid-based, Grid-based, bounded, and bounded, and rectangular rectangular environmentenvironment

If the fish leaves If the fish leaves on one side, it on one side, it re-enters from re-enters from the other side the other side (toroidal)(toroidal)

Part 2: WrappingEnvPart 2: WrappingEnv

Students learnStudents learnTo reuse existing code by subclassingTo reuse existing code by subclassing

To integrate new code into a frameworkTo integrate new code into a framework

Students’ code still based on existing Students’ code still based on existing codecode

But cannot simply be copied and modified But cannot simply be copied and modified anymoreanymore

Part 3: InternalsPart 3: InternalsCode missing in several places of the Code missing in several places of the frameworkframework

Students reimplement critical portionsStudents reimplement critical portionsGives students a tour of the entire frameworkGives students a tour of the entire framework

Unit tests provide guidanceUnit tests provide guidanceError messages in plain EnglishError messages in plain English

Strategy Pattern

+ void move()

+ void move() + void move()

Static Behavior! Separate the variants from the invariants

Part 4: Behavior StrategiesPart 4: Behavior Strategies

Part 4: Behavior StrategiesPart 4: Behavior Strategies

Students have the opportunity toStudents have the opportunity toApply design patterns to improve the projectApply design patterns to improve the project

Refactor a substantial portion of the codeRefactor a substantial portion of the code

Experience how loose coupling makes this easyExperience how loose coupling makes this easy

Requires new design and code that Requires new design and code that augments existing frameworkaugments existing framework

Assignments in Objects-FirstAssignments in Objects-FirstAssignments have to be rich and deepAssignments have to be rich and deep

Highlight benefits of object-orientationHighlight benefits of object-orientation

Large design portionLarge design portionFind proper abstractions, variants / invariantsFind proper abstractions, variants / invariants

Solve family of problemsSolve family of problems

Challenge to find suitable assignmentsChallenge to find suitable assignmentsMust be within students’ graspMust be within students’ grasp

Milestone 2 due today!Milestone 2 due today!

The Culmination of a The Culmination of a Unified OO PedagogyUnified OO Pedagogy

Abstract Structure and BehaviorAbstract Structure and Behavior

PolymorphismPolymorphism

Design PatternsDesign Patterns

Unit TestsUnit Tests

MBSMBS ~ end of 2nd semester.