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Hello PigWorld

Hello PigWorld. Raymond Lister University of Technology, Sydney. Pigworld. Boy Pigs and Girl Pigs. - Note the rope. Pig Controllers. Pig Food and Food Trees. When a boy meets a girl … . Before. After. Class Hierarchy: Complete – 41!. Animal / Vegetable / Mineral.

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Hello PigWorld

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  1. Hello PigWorld Raymond Lister University of Technology, Sydney

  2. Pigworld

  3. Boy Pigs and Girl Pigs - Note the rope

  4. Pig Controllers

  5. Pig Food and Food Trees

  6. When a boy meets a girl … Before After

  7. Class Hierarchy: Complete – 41!

  8. Animal / Vegetable / Mineral

  9. Model / View / Controller • Views largely explain the • plethora of classes • Students don’t generally • read them. • Only one controller class, • “AnimalController”

  10. Transcending the dialectic In the procedural style, algorithms are encoded explicitly within the methods of an object, but … in the object oriented style, algorithms emerge implicitly from the interactions between objects.

  11. Find the minimum/maximum: the one essential procedural algorithm • while ( not finished ) { get next element; if ( smaller/larger than previous best ) remember this new best element; } • Algorithm originally taught without reference to PigWorld, as finding the minimum / maximum of a sequence of inputted numbers. • Students then adapt basic algorithm to uses within PigWorld (e.g. radar and look for food)

  12. Note! • Not banning all algorithms more sophisticated than finding minimum / maximum. • More sophisticated algorithms may be implemented as interactions between objects. … for example …

  13. Dijkstra and the “Oink” Algorithm • “Oink” is Dijkstra’s • shortest path • algorithm. • Of the students who • attempted the • assignment, 88% • completed this task • (ie. 42% of class).

  14. By the way … • Emphasize message passing between instances of the same class to reinforce basic concepts (especially class vs. object) • Transmission of sound does that nicely

  15. Rope and Linked Lists • Doubly linked list. • Students given code to play out • rope. Assignment task was to • destroy the rope of a pig. Of those • who attempted the assignment, 82% • completed this task (ie. 39% of class). • Recursion NOT required. Done by • message passing.

  16. Once again … • Emphasize message passing between instances of the same class to reinforce basic concepts (especially class vs. object) • Destroying rope does that nicely

  17. Teach Linked Lists before Arrays • Teaching linked lists early reinforces: • Message passing • Objects versus classes • Arrays are a distraction from the above key concepts: • Come with their own syntax

  18. Re-use Classes(Animae)

  19. Re-use Classes(Animae)

  20. Want to Know More? Lister, R. (2004). Teaching Java First: Experiments with a Pigs-Early Pedagogy. Sixth Australasian Computing Education Conference (ACE2004). Dunedin, New Zealand. January 18-22. pp. 177-184. In the ACM Digital Library. Email me if you’d like to have the code.

  21. c.f. Greenfoot • http://www.greenfoot.org/ … • “Consider greenfoot as a combination between a framework for creating two-dimensional grid assignments in Java and an integrated development environment (class browser, editor, compiler, execution, etc.) suitable for novice programmers.” • The existing implementation of PigWorld is a little clunky; a re-implementation within Greenfoot would be ideal.

  22. Conclusion (1):Assignment design principles • Emphasize message passing between instances of the same class to reinforce basic concepts (especially class vs. object) • Use only simple loops that search for smallest or largest values in a sequence. • Teach linked lists before before arrays. • Ideally, don’t even teach loops in semester 1 • Reuse classes

  23. Conclusion (2): Transcend the OO vs. Procedural dialectic In the procedural style, algorithms are encoded explicitly within the methods of an object, but … in the object oriented style, algorithms emerge implicitly from the interactions between objects.

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