READ the entire sheet of the Scheme Drawing Commands.
NOTE: Colors start with a single quote. Identifiers
in DrScheme are case sensitive. Commands are usually all lower-case
Look at the back of the handout and REVIEW the example program. If you have a programming error found in the interaction window, you can check the "Book of Errors" to help you debug your program.
Open the DrScheme IDE, click on Language, drag down to clear pack, then
click on the icon called execute. You will see that the teach packs will
be cleared. Then click on language again. Drag down to Add / teachpack.
Then you will see a folder that says htdp. Double click on it. You
will see a bunch of different packs. Find the one that says draw.ss,
click it and press open. Click Execute
If the drawing teach pack is not added, you get the error message: reference to undefined identifer start.
Type the first command: (start 640 480). This creates a canvas
that is 640 pixels across and 480 down. The top left corner is (0,
0), like a flipped over quadrant I on a Cartesian plane. Get a piece of
graph paper and start numbering lines to use for planning your picture.
Use whatever proportion you would like. Easier if every line is worth
10 pixels and you only number only every 5th or 10th line.
After typing the first command, press execute. Then "bam!" you
will see the drawing canvas.
OFTEN! Create a folder called "scheme"
in your server folder. Save using a descriptive identifier such as babyYourName.
The computer will add the file extension .scm automatically. When
you are finished, back up the program to your USB memory stick.
Start the first constant definition for the HEAD by typing the header and
the first two lines.
Keep )) at the end or you will get the error “malformed define” as you
add new lines of code.
(draw-circle (make-posn 320 100)
44 'black); head outline
(draw-circle (make-posn 300 95)
8 'green); left eye
... Add new lines of code here....
Close out the parenthesis. You will
see the lines highlighted until you get past the header. HINT: Select
all the code, then hit the tap key and the spacing will be formatted automatically.
This help in debugging your code.
Click Execute. If you do not see any drawing check your code and
click execute until you will see a picture that matches the code. Make
sure you type the correct coordinates and always begin and end the phrase
with parenthesis (remember the “dance”).
Document each line of code so you know what the command is producing (See italics in above code example). Plot the points for the head circle and rectangular body on your graph paper. ESTIMATE the
location, it does not need to be exact. Try to plot other coordinates if you do not understand the connection, or ask for help. As you get into planning
your own program, you can adjust on the computer code. The top left
corner is (0, 0), the bottom left is the size of your canvas. X is
plotted the same, but Y is backwards as it increases as you go down instead
of like quadrant I in a Cartesian plane. The objective is to learn the
patterns and the code. Continue adding one line at a time and plotting
the points. Check your progress by clicking execute and looking at
Once you are finished with typing all the code on the sample program,
you should know how to plan a program for the Balloon picture and to use
the drawing commands.
Change the color of the shoes to something
different and the color of the shirt to something different. Also, add some hair. Raise
your hand and show for a grade. Enhancement: Add
some more decoration to the object.