These essentials are on page 100 (PDF page 111) or page 138 (PDF page 149). There is a detailed checklist on page 105 (PDF page 116). Use it! You should memorize them.
model
: What the computer remembers.
draw-handler: model -> image
: Draw the model on the screen; adds non-moving parts to the image. (on-draw
)
tick-handler: model -> model
: Update the model as time passes. (on-tick
)
key-handler: model key -> model
: Update the model when a key is hit. (on-key
)
mouse-handler: model x y event -> model
: Update the model when the
mouse is moved or clicked. The inputs x and y are numbers, the event is a string. (on-mouse
)
When designing every function, these are the steps you should follow:
Reference: page 70 (PDF page 81) has a longer version of the same list.
Q: Why do you write “model” when the model is just an image?
A: Next chapter our models will be numbers, and soon after that our models will be sentences. If you memorize “model” as the type, you don’t need to memorize a new signature every chapter.