1. Chapter 2: Programming in Alice

2. Chapter 2 Objectives To understand: method naming conventions
what dot notation is
what a primitive method is and which objects have them
what is meant by “calling”
what an argument is in a program.
differences in naming conventions
the steps of the program development cycle
what a logical error is
the need for commenting

3. Lessons Writing Methods Naming Conventions Designing a Program
Comments
Tips for Setting Up an Initial Scene
Executing Instructions Simultaneously
Exporting Your Code for Printing

4. 2.1 Writing Methods
In chapter 1 we learned the basics of placing objects in an Alice world and then manipulated the way those objects appear.
The worlds did not perform any actions.
If we want the objects in an Alice world to perform actions, we have to write a program.

5. Writing Methods What is a method? set of instructions that execute
2.1
Writing Methods
What is a method?
set of instructions that execute
create methods by dragging tiles into the Method Editor
these tiles are the instructions
my first method

6. the period is called a “dot”
2.1
Naming Conventions
All methods have a name.
dot notation
world.my first method
dot (period) separates pieces of information
left side: object that the method belongs to in this case…the method belongs to the WORLD object
right side: name of the method in this case… “my first method”
the period is called a “dot”

7. 2.1
world.my first method
Events Editor identifies which method plays or is acted upon when the “Play” button is hit

8. tile world.my first method
2.1
world.my first method
Methods play the instructions (tiles) that are dragged into the Method Editor
Each tile represents an action that will take place when the world is played.
tile

9. 2.1
Primitive Methods
All objects have a common set of built-in method for performing actions.
These “primitive methods” all objects to move, turn, change size, and more.
Example: Hare has primitive methods: move, turn, roll, resize, say, …
Name of object.Name of method

10. Adding a Method to a Program
2.1
Adding a Method to a Program
Highlight the object, drag and drop the method into the Method Editor, select the arguments.

11. Adding a Method to a Program
2.1
Adding a Method to a Program Or
Right click on the object, choose the methods menu, choose the method from the list, choose the arguments

12. Terminology argument argument method object editing tag
2.1
Terminology
Calling the method Executing a method
Argument:
piece of information that a method needs in order for it to execute
hare.move…which direction? the direction…up, down, left, right…is the argument
Passing the Argument:
the method is called and the arguments are presented
argument
argument
method
object
editing tag

13. Editing Tag Holds additional arguments
2.1
Editing Tag
Holds additional arguments
What appears depends on the method called
duration is a common one specifies amount of time for action to take place default (1 second)

14. Table 2-1 summarizes all the primitive methods.
2.1
Table 2-1 summarizes all the primitive methods.
orient to
turn to face
point at
set point of view to
set pose
stand up
move at speed
turn at speed
roll at speed
constrain to face
constrain to point at
move
turn
roll
resize
say
think
play sound
move to
move toward
move away from

15. Deleting Instructions
2.1
Deleting Instructions
Right-click the instruction and select delete or
Drag the instruction tile to the trash can

16. Copying Instructions Right-click the instruction and select copy
2.1
Copying Instructions
Right-click the instruction and select copy
Drag the instruction tile to the clipboard
when the clipboard turns green, drop the tile
click on the clipboard and drag it back to the Method Editor

17. 2.1
Custom Methods
In addition to primitive methods (the things that ALL objects can do)…some objects have custom methods
Custom methods are methods that only objects of a specific class can do.
When objects is selected from gallery, a listing of custom methods appears.
Names of the custom methods give clues as to what the method does.
What do you think the foottap custom method does?

18. 2.1
Custom Methods
When you add an object and then select that object, tiles representing its custom methods (if it has any) appear above the tiles for the primitive methods in the Details Panel.

19. 2.1
p. 62 Tutorial 2-1
Happy Hare
aka Hare jumps up then down.

20. p. 67 Tutorial 2.2 Really Happy Hare
2.1
p. 67 Tutorial 2.2
Really Happy Hare
aka hare jumps up, spins around, comes down, and says “that was fun”

21. 2.1
Checkpoint p. 72
1. In an Alice world you have an object named hare. The hare object has a method named move. How would you write the method name using dot notation?
2. What causes a method to be executed automatically when a world is played.
3. What is a primitive method?
4. How do you see a list of the primitive methods that an object has?
5. When specifying a distance for the move method, what happens when you select other…. from the menu? When would you use this selection?

22. Checkpoint p. 72 continued
2.1
Checkpoint p. 72 continued
6. A fellow classmate has placed an instruction in the Method Editor. You ask her what the method does, and she says, “It calls another method.” What does she mean by that?
7. What is an argument?
8. What is a custom method? Do all classes provide custom methods?
9. How can you see a list of the custom methods that a class has?

23. Which one coaches the Mustangs and which one coaches the Eagles?
2.2
2.2 Naming Conventions
Names are known as identifiers…because they identify items in a program.
Use a name that provides meaning
Name of method should indicate the method’s purpose.
Which one coaches the Mustangs and which one coaches the Eagles?

24. namingConventions Most programming languages do NOT recognize spaces.
2.2
namingConventions
Most programming languages do NOT recognize spaces.
Alice allows spaces method.my first method
Since spaces are not allowed, how do you combine more than one word in naming?
Capitalize subsequent words
Called camelCase
Note the space
Note the space
Which is easier to read?
onehumpcamel or
oneHumpCamel 24

25. Class Names method names begin with a lower case letter
2.2
Class Names
method names begin with a lower case letter
Class names are capitalized
No spaces, so each word is capitalized
This convention is called PascalCase

26. Renaming Objects Methods
2.2
Renaming
Objects
Right-click object’s tile in the object tree and select rename.
Methods
Select the world object
Select the method’s tab from the Details Panel
Right-click the my first method tile and select rename.

27. Checkpoint p. 77
10. Why is it important that you give meaningful names to objects?
11. In most traditional programming languages, it is acceptable to have spaces in object or method names?
12. What is the camelCase naming convention? When is it used?
13. What is the PascalCase naming convention? When is it used?

28. 2.3
2.3 Designing a Program
Design the program
Write the methods
Test the methods
Debug the methods
Design requires planning…that follows the above steps
Called Program Development Cycle
Cycle is repeated until NO errors appear in the program.

29. Designing the Program Determine what the world is supposed to do.
2.3
Designing the Program
Design the program
Write the methods
Test the methods
Debug the methods
Determine what the world is supposed to do.
Read a problem statement that describes the which objects will appear in the world, and the actions that are to take place.
What is the “Story”? 29

30. 2.3
Designing the Program
Design the program
Write the methods
Test the methods
Debug the methods
Break the problem statement down into series of steps
Pseudocode or
Flowchart 30

31. 2.3
Writing the methods
Design the program
Write the methods
Test the methods
Debug the methods
Design steps (pseudocode or flowchart) provides model for writing the methods
Drag tiles into Method Editor to assemble instructions
Instructions should follow the order of the Design steps
Pseudocode and flowchart may NOT be at the detail of the final instructions 31

32. Testing Test to make sure it meets the following criteria:
2.3
Testing
Design the program
Write the methods
Test the methods
Debug the methods
Test to make sure it meets the following criteria:
Does it do what it was intended to do?
Does it have any errors? Any undesired results?
Is it efficient? Are there unnecessary steps?
If the criteria are NOT met, then debugging occurs 32

33. 2.3
Designing a Program
Design the program
Write the methods
Test the methods
Debug the methods
Debugging means to determine what must be corrected or modified to get the program to work correctly
Logical errors (bug) is a mistake that produces an incorrect result, but the program still runs.
Instructions in an incorrect order may produce incorrect results
Passing incorrect values as arguments can cause logical errors 33

34. Tutorial 2-3 Using the program design cycle
2.3
Tutorial 2-3
Using the program design cycle
Story: Recreate the opening scene of Lewis Carol’s Alice’s Adventures in Wonderland.
Alice sees White Rabbit run by her, saying to itself, “Oh dear! Oh dear! I shall be late!”

35. 2.3
Checkpoint p. 87
14. What are the steps in the program development cycle?
15. What are two tools that you can use to break down a problem into a series of steps?
16. What is a logical error?
17. When testing a method, what are three criteria that you should make sure the method meets?

36. 2.4 Comments //comment tile A comment is a note explaining the code.
Crucial part of the code.
Makes the code understandable.
Alice ignores comments when it plays your program.
//comment tile

37. 2.4
Tutorial 2-4
Inserting Comments

38. Checkpoint p. 90 18. Why are comments important?
2.4
Checkpoint p. 90
18. Why are comments important?
19. Do comments affect the way a program runs?
20. What symbols appear on the comment tile in Alice? Why were these symbols chosen?

39. 2.5 Tips for Setting Up the Initial Scene
Use the primitive methods to setup the scene.
Select the object in the Object Tree, then select a method.
Use the primitive methods to position the objects.
Doing so from the Object Tree positions the objects outside of the program.

40. Tips for Setting Up the Initial Scene
2.5
Tips for Setting Up the Initial Scene
Moving an object to the center of the world
Use the move to method and choose the entire world as the method’s argument
Places the object’s center point at the world’s center point of (0, 0, 0) 40

41. Tips for Setting Up the Initial Scene
2.5
Tips for Setting Up the Initial Scene
Positioning objects a specified distance apart
Use the move to method and choose asSeenBy the other object for the method’s argument
Places the object’s center point at the world’s center point of (0, 0, 0) 41

42. Tips for Setting Up the Initial Scene
2.5
Tips for Setting Up the Initial Scene
Moving the camera to an object
Right-click the object and choose Camera get a good look at this
Camera moves to a position so the object is in plain view 42

43. 2.6 Executing Instructions Simultaneously
By default, instructions are executed one after the order…in the order they appear in the Methods Editor
For simultaneous actions, drag Do together into the Methods Editor
Other instructions can be placed within the Do together tile
Make sure the duration for all items in a Do together are the same

44. The Do in order Structure
2.6
The Do in order Structure
By default, all instructions are performed in order they appear in the Methods Editor
Do in order structure used when more than one set of actions must occur simultaneously…but has steps that must be done in order

45. Tutorial 2-5 Creating simultaneously executed instructions
2.6
Tutorial 2-5
Creating simultaneously executed instructions
Story: Two penguins (a brother and a sister) are facing each other, 2 meters apart. The brother penguin says, “Hey sis!”. Then the sister penguin says, “Hey brother!” Then the two penguins simultaneously move ½ meter toward each other and stop. Then they simultaneously jump in the air.

46. 2.6
Checkpoint p. 104
21. How do you cause instructions to execute simultaneously?
22. How can you cause some of the instructions in a do together structure to be executed in order?

47. 2.7 Exporting Code for Printing
Code can be exported to an HTML file
Open the file and Print
From File – Choose Export Code for Printing
You must add your name as the author
Author’s name is printed with the exported code
Author’s name

48. Review Questions p. 105
Short answer p. 107

49. Exercises 1. Scene from Alice’s Adventures in Wonderland
2. Animated Underwater World
3. Magic Cookies, Part 1
4. Magic Cookies, Part 2
5. Animal and Bicycle
6. Drag Racing
7. Playing Ball
8. Dancing
9. Apollo 15 Experiment
10. Tables, Chairs, and a Magic Broom
11. Movie Scene