Teaching With Alice First Bytes Teachers Workshop July 2008 Topics What is Alice?

Teaching With Alice First Bytes Teachers Workshop July 2008

Topics

• What is Alice?

• What resources are available?

• How is Alice used in teaching?

• Demo of Alice programming

What is Alice?

• Alice is a visual programming language.

• Alice is an object based language. The objects in Alice are 3 dimensional models.

• The output of Alice programs are 3 dimensional movies.

Visual Programming

• Programming is done by pointing and clicking, dragging and dropping, selecting from menus, and some typing

• Syntax errors removed from the equation

• no braces, no semi colons

Object Based Programming

• Built in library of models.

• More available on the web.

• All objects have certain methods and behaviors

• move, turn, say, roll, resize

• New methods can be added to an object

• object can be saved as a new class

• Polymorphism is not supported.

Alice Models

• Main programming data are 3d models

• Many built in and more on web

Output

• Output are 3d movies

• run the program, play a movie
• can also add sound to programs

• A lot easier to recognize logic errors

• "Why do my ninja's arms keep flying away?"

Alice Resources

• Main page

• www.alice.org

• download Alice 2.0 for free

• story telling Alice for middle school

• Models gallery

• Forums

• Textbooks list

Instructional Materials

• www.aliceprogramming.net

• Password protected

• userid:
• password:

• Workshop schedule

• Example course calendars / syllabi

• Slides and sample worlds

• Solutions to chapter exercises and projects (Dann, Cooper, Pausch book)

• Sample exams and test bank questions

Even More Materials

• Dick Baldwin, ACC teacher

• www.dickbaldwin.com
• www.dickbaldwin.com/tocalice.htm

• Lots of materials and "how to's"

• Alice newsletter. To sign up contact Barbara Conover

• [e-mail]

How is Alice Used in Teaching

• Originally designed for students in middle school

• Has been successful with older students

• Used in lots of types of courses

• computer literacy
• pre cs or pre AP
• cs1 or APCS
• programming for non CS majors

Approaches

• Cover basics, chapters 1 and 2 quickly

• learning the tool

• Paths through intro programming

• objects early (control structures first)
• objects first
• objects first, recursion early

• Interactivity

• can create animations / movies only
• OR introduce events and interactivity

Projects

• Closed-ended

• write a program to meet specified criteria
• allows focusing on some aspect of programming
• closed-ended with options - charades

• Open-ended

• some students show great creativity here
• some make very skimpy programs
• chance to require storyboarding and planning

Sample Program - Bunny and Broccoli

Demo of Alice Programming

• Follow along!

• Problem solving and programming in Alice

• given a scenario create program to enact the story

• A bunny is sitting in a field. Around the bunny broccoli sprouts and grows. The bunny hops over to the closest broccoli plant and eats it.

Create a New World

Select Template (Ground)

Add Objects

The Scene Editor

Beware the Scene Editor

• Students can spend A LOT of time in the scene editor setting up and tweaking a world

• Is that really programming? Or computer science? Or Computational thinking?

Add Objects

• Drag and Drop

• Click on picture then click on Add Instance

Objects in The World

• Objects in Alice

• Have their own frame of reference
• forward – backwards
• up – down
• left – right

Frame of Reference

• Clicking on object bring sup its bounding box

• Can also see center point

• .. and axes

Frame of Reference

Camera Controls

Mouse Control Tools Kit

Subparts

• Objects often have sub parts

• may have their own frame of reference

• Clicking affect subparts box allows selection and movement of subparts

Subparts

• Bigger ear

Alternate Positioning Techniques

• Right click on object in world on object tree and select method

• Drag and drop method from the details panel.

Quad View

• Use world's absolute frame of reference to view relative position of objects

Finding Objects

• To reposition in a quad view

• select zoom in and out from mouse controls
• zoom way out
• select scroll from mouse controls to center objects
• zoom back in

Setting Up Initial Scene

• Add bunny

• Add broccoli

• local gallery -> kitchen -> food

• Make broccoli bigger

• Move broccoli below the ground

• How to simulate "growing"?
• move down exactly 1/2 meter using drop down menus or drag and drop

Moving Broccoli Down

Making Broccoli Invisible

• In our program we want the broccoli to grow.

• We will do this by having it

• move up
• get bigger
• become visible

• Need to make the broccoli invisible

• Select each broccoli from the object tree and click the properties tab

• Change opacity from 100% to 0%

Back to Programming View

• When setup complete click the green done button to go back to the programming view.

Programming the World

• From a storyboard to a program.

Recall the Storyboard

• A bunny is sitting in a field. Around the bunny broccoli sprouts and grows. The bunny hops over to the closest broccoli plant and eats it.

• Let's add some detail at the start of the movie.

• The bunny first turns to fast the camera. Then the broccoli start to grow and while it grows the bunny hops up and down.

Methods

• Select the world object from the object tree and the methods tab in the details panel.

• The world starts with a single method, "my first method"

• Like main in a Java or C++ program.

Adding Commands to Methods

• If the "my first method" is not displayed in the code editor click the edit button next to the method in the detail panel.

• Commands are added by dragging and dropping them into a method.

• Select the bunny from the object tree.

• Drag the turn to face command into the code editor.

Adding Commands

• turn to face is a method

• When adding a method to the code editor if any parameters are required a menu pops up to select the arguments.

• Select the camera.

More Parameters

• After adding the bunny.turn to face command the "my first method" will look like this:

• Click on the "more" option to see what other parameters can be changed

• duration, style, asSeenBy
• change duration to 3 seconds

Test

• Click the play button to see the movie / output of the program.

• "my first method" will execute because of the only event in the program at this point.

Adding Behaviors

• Next we want the bunny to hop while the broccoli grows.

• Methods can be world level or class level.

• world level methods belong to the world.
• a method should be world level method if it involves two or more objects
• class level methods belong to a particular class / object.
• a method should be a class level method if it involves only one object

Creating a Hop Method

• The bunny does not have a hop method so we will create one.

• Select the bunny from the object tree and click on the create new method button in the details panel.

Creating a Hop Method

• A window pops up asking for the name of the method

• try various names to see what is a legal identifier and what is not

• After giving the new method a name a new tab pops up in the code editor

• Should hop be one hop or parameterized?

• Should parameter be time to hop or number of hops to make?

• Any other way to make it more general?

Adding Parameters

• Let's add parameters for distance to hop up and the time to do the hop

• Click the create new parameter button in the code editor.

Adding Parameters

• Give the parameter a name and pick the data type

• distance -> a Number
• time -> a Number

• When called the hop method now requires two parameters

Adding Commands to Hop

• To hop the bunny will move up and then down.

• Drag the move command into hop and fill in the parameters.

• Drag another move command into hop and fill in the parameters.

Adding Commands to Hop

• To change the duration of moving up select the more option from the move command.

• Select duration then expressions then time (or the name of your parameter for time)

Adding Commands to Hop

• To change the duration of the move to half of the time parameter click on the triangle to open the drop down menu.

• Select math and divide time by 2.

• Do the same for the move down.

Completed Hop Method

Back to my first method

• We want the bunny to hop while the broccoli grows

• In the initial set up the broccoli is below the ground and invisible

• The broccoli will grow by

• moving it above the ground
• resizing it to double it original size
• making it visible

A grow Method

• Instead of repeating the actions to grow for each broccoli we will put it in a method

• could make a class level method and then save a new broccoli object that knows how to grow and add two of those to world (inheritance)
• OR make a world level method and send in each broccoli as a parameter

• We'll take the second option

A grow Method

• Create a new world level method named grow

• Add a parameter of type Object

• Common mistake is to not change parameter type to correct type.

Adding Commands to Grow

• We want all three things (move up, resize, and become visible) to happen at the same time

• Default for commands is in order

• Do together is a primitive that executes commands together

• Drag and drop a Do together into the grow method

Do together

• Commands in a Do together block will be executed in parallel

• Each command can have a different duration

• Do together completes when last inner command completes

Growing

• Drag and drop the parameter from the method header into the Do together block and select the methods to

• resize
• move up

• Change duration to 5 seconds for each

Becoming Visible

• Properties may be changed as program commands

• A little tricky to do with parameters

• Select any object from the object tree and its properties tab

• Drag the opacity property into the program and select 100%

Becoming Visible

• Now replace the object that we dragged into the grow method with the parameter by dragging and dropping.

Completed grow Method

Back to my first method

• Now that the bunny can hop and the broccoli can grow we can complete the first part of the story board

• After the bunny turns to face the camera we want the broccoli to grow and the bunny to hop all at the same time.

growing and hopping

• Drag a Do together block into my first method after the bunny turns to face the camera

• Drag the grow method into the Do together block three times and add pick each broccoli once for a parameter

Testing

• Test the program by pressing the play button.

• Is anything wrong?

Resizing and Moving Up

• Resizing the broccoli has altered the distance of its center point below the ground

• Some of the broccoli's stalk is still below the ground

• Go back to grow method and alter the amount to move up to a value that makes more of the broccoli appear above the ground

Hopping

• We want the bunny to hop while the broccoli grows

• Back to my first method

• Broccoli takes 5 seconds to grow

• Have rabbit hop up and down .25 meters at 0.5 seconds per hop

• How many hops?

Looping

• A counted loop is used when the number of repetitions can be calculated

• Drag a Loop primitive into the Do together block

• Number of times to loop is 10

Hopping

• After Loop is added to Do together drag and drop the bunny hop method into the loop

• Select 0.25 meters for distance to hop and 0.5 seconds for time

• Test!

Eating the Closest Broccoli

• Now we want the rabbit to turn to face the closet broccoli, hop over to it, and eat it.

• Which broccoli is closest?

• We want to be able to reposition broccoli and not have to change program

• Create a function !

Creating Functions

• Functions, unlike methods, return an answer.

• Sometimes called questions.

• Create a function to return the broccoli that is closest to the bunny.

• Select the world in the object tree and the function tab in the detail panel

Create a New Function

• Click the create new function button .

• Give the function a name.

• Pick the data type for what the function will return.

• In this case an Object.

Which Broccoli is Closest

• Decision making for which broccoli is closest

• When is broccoli1 closest?

• Drag an if/else into the function

• Initial condition doesn't matter.

Condition of if/else

• Select world in object tree and function

• replace true in if/else with a function

• Initial values don't matter

Checking broccoli1

• Click on broccoli1 in the object tree

• Replace the first value in the a with the function broccli1 distance to

• Select the bunny as the parameter

Checking broccoli1

• Replace the second value of a

• Multiple ways to go from here

Checking broccoli1

• One option, AND

• Bring up drop down menu on expression, select logic and then the and option

Checking broccoli1

• replace the value after the and with the world level function a and then compare broccoli1's distance to the bunny to broccoli3's

• results in a long Boolean expression

• if true, return the broccoli1 object

Checking Other Broccoli

• in the else, repeat for broccoli2

• make the last return broccoli3

Calling closestBroccoli

• Go back to my first method.

• Select the bunny and drag a turn to face command.

• Pick expressions and then the function closestBroccoli for the argument.

Test

• Test function by playing movie

• Test further by changing initial set up of broccoli to change which broccoli is closest

my first method

Hopping Forward

• Create a new method hopForward

• Parameters for total distance and distance per hop

• lots of other ways to do this

Completing the Hopping

• Back in my first method call the hopForward method.

• Pick a dummy value for totalDistance.

• Replace dummy value with distance from bunny to closestBroccoli minus some offset. (no collision detection)

Eating Broccoli

• Make closestBroccoli disappear

• Could add some motion to bunny

Complete my first method

What Next?

• Expand by adding more broccoli

• lists and variables to manage

• Add sounds

• Add scenery

• Add events

• Interactive programs can be created by adding events that program responds to.