Loops and a Short Intro to Joysticks, DDR Dance Pad and other Strange Hardware

Loops: The Basics

Loops are one of the main building blocks of programming/scripting (just like the "if... then" conditionals we've looked at so far).
Loops repeat a certain piece of code for a certain time, until a condition is met, or they may repeat forever.

Frame Loops / Looping in a Frame

We've already used the fact that Director loops within a frame to create, for example, the illusion of motion. example.dir

property p_clicked

-- when the viewer/user clicks on the sprite for the first time p_clicked = 1 - the mostion starts.
-- If they click the second time p_clicked switches to 0 and the motion stops
on mouseDown me
        if p_clicked = 1 then
                p_clicked = 0
        else
                p_clicked = 1
        end if
end

-- this is the loop, it happens everytime the playhead exits the Frame (on exitFrame)
on exitFrame me
        if p_clicked then
                sprite(me.spriteNum).rotation = sprite(me.spriteNum).rotation +10
        else
                sprite(me.spriteNum).rotation = sprite(me.spriteNum).rotation
        end if
end

Exercise: This circle will just grow and grow and grow if you don't build some code that makes it stop on click.
Below the loop script that makes it grow:

on exitFrame me
       sprite(me.spriteNum).rect = sprite(me.spriteNum).rect + rect(-1,-1,1,1)
end

Repeat Loops

The command "repeat" can make loops that are not dependent on the looping of the playhead within one frame.
In behavior scripts they can for example be used to check for changes.
If the loop is extremely elaborate and runnning all the time then it may interfere with audio playback

In this example, once all the sprites have been changed to red by the user, the user is transported to the next scene.
The sequence in which the sprites were changed does not matter - when the last one is changed, the playhead advances.

How do we know when all of them have been changed?

Each time the user clicks one of the sprites, it changes it's member and then iterates through the others to check if there are still unchanged ones.

Iteration is done by loop:
the following script just changes the member of the sprite
then it loops through all the sprites and prints their member number into the message window

on mouseUp me
       sprite(me.spriteNum).member = 2

       repeat with i = 1 to 9
               put sprite(i).member
       end repeat
end

of course, this is not enough, we need to add some conditionals
so that we can control what the script does when it finds out that NOT all sprites have been changed.

on mouseUp me
       sprite(me.spriteNum).member = 2

       repeat with i = 1 to 9
              if sprite(i).member <> member(2) then
                    exit repeat
              end if
       end repeat
end

The "<>" is the opposite of "=" and means "is not equal". These are called Comparison operators.
This script checks the member number of each sprite. The code is repeated 9 times. Each time, the variable i is one number higher than before. So the first time the loop is executed, the script checks sprite(1), then sprite(2), sprite(3) etc.

When the script finds a sprite(i) that has not been changed to member(2), it jumps out of the repeat with "exit repeat" and does nothing else.

But what if we want it to actually jump forward when it finds that that it has arrived at the ninth iteration of the loop and finds that all the sprites have changed to member(2) ?

on mouseUp me
       sprite(me.spriteNum).member = 2

       repeat with i = 1 to 9
              if sprite(i).member <> member(2) then
                     exit repeat
              else if sprite(i).member = member(2) and i = 9 then
                    go to marker("scene2")
              end if
       end repeat
end

Like this you could for example do a simple memory game example

Here is a snippet out of the memory game (the whole thing would be too complicated to cover in an example).

example (with 8 parts)
example (the same with 4 parts)

on mouseUp me

       repeat with i = 1 to 8
              if sprite(i).member <> member(3) then
                    counter = counter + 1
              end if
       end repeat

       if counter >= 2 then
             repeat with i = 1 to 8
                     sprite(i).member = member(3)
              end repeat
              counter = 0
       end if

sprite(me.spriteNum).member = member(2)
sprite(me.spriteNum).ink =136


end

Sprite within... / intersects properties (this does not have anything to do with looping - but might be useful)

on exitFrame me
    if sprite sprite(2) within sprite(me.spriteNum) then
        member(4).text = "perfect"
    else
        member(4).text = "drag the circle into the rectangle"iiiiiiii
    end if
end

The "sprite...intersects" property checks if one sprite touches the other. .
(Note: i am not using the dot syntax here because i think that this particular property is easier to understand in the verbose syntax)
example

on exitFrame me
    if sprite sprite(2) intersects sprite(me.spriteNum) then
        member(2).text = "OUCH! NOT THAT CLOSE!"
    else
        member(2).text = "DRAG THE CIRCLE CLOSER TO ME!"
    end if
end

example

Joystick Xtra

download from here http://pro.wanadoo.fr/freextras/index_en.html#JoystickXtra -- this one only works on PC / there are some non-free ones that work on both mac / pc

Drop the Xtra in the Xtras folder which can be found in the Director Application folder.

it comes with an example that lets you test the functionality of your joystick / gamepad / Dance PAd

if you have a playstation 2 dance pad there is a usb adapter for pc

Jeff will do a Joystick demo in class on monday...