The Tiles and SB-World Teachpacks

These teachpacks provide a variety of functions for manipulating and animating graphical images. To use them, you'll need to

download them to your computer,
install them in the right place in your computer, and
load them in DrScheme.

By the way, there are more up-to-date versions of these teachpacks, somewhat easier to install and use, but the following directions are for the versions installed in our classroom.

To download and install

This should be done once on your home computer, and you'll never have to do it again. You shouldn't need to do this at all on a classroom computer.

Right-click on this link) and choose "Save Link" (or the equivalent on your browser). Save the file someplace like the desktop; we'll clean that up later.
Do the same with this link.
Start DrScheme.
If it doesn't say "Language: Beginning Student", go to the "Language" menu, then "Choose Language", then "How to Design Programs", then select "Beginning Student". Click the "Run" button.
If it says anything about "Teachpacks" on the line below "Language: Beginning Student", go to the "Language" menu and "Clear All Teachpacks". Click "Run".
Go to the "Language" menu, "Add Teachpack", then "Add Teachpack to List", then browse to wherever you put the two files. Double-click one of them and click "OK".
Repeat the previous step with the other file.
Click "Run". You should see something like
Welcome to DrScheme, version 4.1 [3m].
Language: Beginning Student custom.
Teachpacks: 371-tiles.ss and 371-sb-world.ss
If the two teachpacks are listed in the other order, that doesn't matter.
You should now be able to delete the two files from the desktop or wherever you put them.

To load in DrScheme

When you start DrScheme, you can tell it you want to use these added functions, and it'll remember that for the next time you start DrScheme on the same computer... unless somebody else using the same computer tells it not to use this teachpack, in which case you'll need to go through these steps again.

Go to the "Language" menu in DrScheme and choose "Add Teachpack", and you should see both 371-tiles.ss and 371-sb-world.ss on the right-hand side. Click one of these, then "OK". Repeat with the other teachpack. Click the "Run" button. You should see a message saying "Teachpack: 371-tiles.ss and 371-sb-world.ss" in the interactions window. The next time you start DrScheme, it should remember this unless you choose "Language->Clear Teachpack" to remove the teachpack.

What do they do?

You can copy-and-paste images from a Web browser into DrScheme and use them just like any other value: you can store them in a variable, etc.

The 371-tiles.ss teachpack

includes several useful functions for manipulating images:

```
image-above: image image ... -> image
```
Combines two or more images into one, putting the first above the second (above the third, ...).
```
image-above-align-right: image image ... -> image
```
Just like image-above, but lines up the right-hand edges of all the images.
```
image-above-align-left: image image ... -> image
```
Just like image-above, but lines up the left-hand edges of all the images.
```
image-beside: image image ... -> image
```
Combines two or more images into one, putting the first to the left of the second (to the left of the third, ...).
```
image-beside-align-top: image image ... -> image
```
Just like image-beside, but lines up the top edges of all the images.
```
image-beside-align-bottom: image image ... -> image
```
Just like image-beside, but lines up the bottom edges of all the images.
```
reflect-vert : image -> image
```
flips an image top-to-bottom.
```
reflect-horiz : image -> image
```
flips an image left-to-right.
```
reflect-main-diag : image -> image
```
flips an image top-right to bottom-left.
```
reflect-other-diag : image -> image
```
flips an image top-left to bottom-right.
```
rotate-cw : image -> image
```
rotates an image 90 degrees clockwise.
```
rotate-ccw : image -> image
```
rotates an image 90 degrees counter-clockwise.
```
rotate-180 : image -> image
```
rotates an image 180 degrees.

The 371-tiles.ss teachpack also includes the image.ss teachpack (which comes standard with DrScheme, so you don't need to worry about installing it). This provides a variety of other functions useful for building and manipulating images in DrScheme. To learn about them, start DrScheme, choose "Help -> Help Desk", and search for "image.ss".

The `371-sb-world.ss` teachpack

provides several functions related to animation:

```
run-animation : number(width) number(height) world(init)
number(tick interval) handler ... -> true
```
This is the most important function in the teachpack. You give it the width and height of your desired animation window, the initial world, how many seconds between "ticks", and possibly some "handlers", and it will run an animation for you. For details, see Chapter 7 of my textbook.
```
run-saveable-animation: ...
```
Just like run-animation, except that it records the sequence of events and allows you to save it as an animated GIF picture.
```
place-image : image number(x) number(y) scene -> scene
```
Puts the specified image at the specified location on the background scene. Note that a "scene" is a special kind of image: any scene can be used as an image, but not every image can be used as a scene. The following two functions provide scenes easily.

nw:rectangle : number(width) number(height) string("outline" or "solid") string(color-name) -> scene

Just like rectangle, but the result is a scene (i.e. its "pinhole" is in the top left corner).

```
empty-scene : number(width) number(height) -> scene
```
Equivalent to calling (nw:rectangle width height "outline" "black"): it creates a white box, outlined in black, of the specified width and height. The easiest way to create a scene.
Handlers

When you run an animation, you can provide handler functions to tell the animation how to do various things: how to redraw the screen from the model, how to change the model at every clock tick, how to change the model when the user uses the mouse or keyboard, etc. Once you've written a function to be used as a handler, you specify what kind of handler it is by calling on-redraw, on-tick, on-mouse, on-key, or stop-when, and passing the result to run-animation.
Redraw handlers

You need to write a function with the contract
model -> image
and install it with on-redraw. This function will be called every time the model changes.

Tick handlers

You need to write a function with the contract
model -> model
and install it with on-tick. This function will be called every time the clock ticks (at the interval you specified in the fourth argument to run-animation).

Mouse handlers

You need to write a function with the contract
model number(x) number(y) symbol(event) -> model
and install it with on-mouse. This function will be called every time the user clicks, releases, or moves the mouse.

Key handlers

You need to write a function with the contract
model char-or-symbol -> model
and install it with on-key. This function will be called every time the user presses or releases a key on the keyboard.

Quit testers
An animation can choose when to stop itself. In the 371-sb-world teachpack, this job is up to the tick, mouse, and key handlers: any one of these can (presumably inside a conditional) call the end-of-time function with a value (typically a string); the animation will end, and that value will be printed out.

Example:
```
(define (dot-at-y y)
    (place-image (circle 3 "solid" "red") 50 y (empty-scene 100 100)))
(define (sub1-or-bust y)
    (cond [(> y 0) (sub1 y)]
          [else (end-of-time "That's all, folks!")]))
(run-animation 100 100 100 .1
               (on-redraw dot-at-y)
	       (on-tick sub1-or-bust))
```

Last modified:

Stephen Bloch / sbloch@adelphi.edu

The Tiles and SB-World Teachpacks

To download and install

To load in DrScheme

What do they do?

The 371-tiles.ss teachpack

The 371-sb-world.ss teachpack

Handlers

Example:

The `371-sb-world.ss` teachpack