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As you come in…
DOWNLOADS FOR TODAY: http://ce21sandiego.org/2013
Alice Project: Wanda Dann and Don Slater, CMU What do you still need (Alice
content/understanding)? (I’ll answer next week…) Index cards As many as you want Counted loops, nested loops, while loops, if
statements, nested if statements, functions, expressions, compound boolean expressions, methods parameters
RSVP: Snacks next week
Wrap up at 5:30 “Snacks and beverages” on the patio
5:30-6:30
Other administrative stuff?
Today’s plan
Methods and Parameters (Probably next time) Lists
Last Time…
Module 2: Make Methods Escape FreakOut Apologize
Did we – add a parameter to our methods? How many times should promGuy spin in
his freakout? What should georgeBeetle say as an
apology? What should promGuy say in his freakout?
One should use methods in programs primarily…
A. For the computerB. For the person writing the programC. For people reading a programD. More than one of the above
And WHY is it important?
How to “make” methods
Think of ways in which your planned animation has natural “parts” Give each of the parts a name Put the code that makes that “part” happen
in a method with that name Call that method from my first method, in
the right order.
Example: Going to a movie…
Walk up to ticket window Walking in group
Buy tickets Interact with ticket seller (talking, hand over
money, get tickets) Enter theater
Walk through doors, hand tickets to worker, walk into lobby
Buy snacks… Take seats… Make snarky critiques… …
Exercise! Choices…
Choice 1: Set up the world yourself, or start with one we set up Do you want practice in setting up world? Focus on methods/parameters
Which exercise: Helicopter Flight Beetle Band
Helicopter Flight [1]
Create a world with a helicopter (Vehicles gallery), airport (Buildings), and a control tower (Buildings).
Part A: Create a circleTower method that makes the helicopter fly
toward the control tower and then around it. In my first method call the circleTower method twice, and then make the helicopter land on the landing strip.
Part B: Modify circleTower to take a parameter indicating how many
times it should “go around” the tower. Change the method call in myFirstMethod to only call the method once, but use a parameter to make it circle 2 time (then try 4 times).
Add another object to the world (maybe a bird or flying dinosaur). Modify the circleTower method to take a second parameter which controls which object should circle the tower.
[1] From Learning to Program with Alice textbook, do not use with students
Beetle Band [1]
Create a world with a stage, and 4 beetles (Animals, Bugs) ringoBeetle, paulBeetle, Lennonbeetle, and georgeBeetle on it. Give them each an instrument (you can pick). Set the instrument’s “vehicle” to their beetle (whoever has that instrument).
Create a method called paulSolo that makes paulBeetle do a “solo” but moving up and down while he spins around 1 revolution. Call this method from myFirstMethod.
Modify the method to be called solo – and control which beetle dances by passing it as a parameter. In myFirstMethod, call solo so that each beetle does his solo in order from left to right.
Modify the solo method to be more flexible by sending a parameter which is the number of spins a beetle should do when soloing
[1] From Learning to Program with Alice textbook, do not use with students
Below: what happens after the last instruction in the mystery method is finished executing?
A. The program starts the World.my first methodB. The program goes back to my first method
and calls method XXXXXC. The program goes back to my first method
and calls method YYYYYD. We can’t tell, we need to know more about the
storyboard to be able to say
If we write a method called drive, which would not make sense as a parameter to control how drive occurs?
A. DestinationB. How fastC. Which carD. Car color
Which of the following is the best explanation of what makes a good parameter
A. It’s something that supports common variation in how the method is done
B. It’s got a meaningful nameC. It can be either an Object or a numberD. It’s helps manage complexity in large
programs