Due date: 1/25 @ 4:30 pm
This problem set is about processing structure
d forms of data.
HtDP Problems:
6.3.1 (1,3,5), 6.4.1 (1,3,5), 6.5.1 (1,3,5), 6.4.2
Additional Problem 1:
Here is a data definition for keeping track the date on an
electronic calendar (which we know is a computer with a display
attached to it):
(define-struct calendar (year month))
;; Calendar = (make-calendar Number Number)
;; Constraints:
;; The first number is always positive for the current year
;; The second number is always between 1 and 12 for the current month.
;; Examples:
(make-calendar 2000 1) ; Jan 2000
(make-calendar 1979 2) ; Feb 1979
Develop the function next
, which advances to the next
month Keep in mind you may have to change year
as well.
Modify the data definition so that Calendar
also keeps
track of days. Then modify next
. The new constraint
is that day
must be greater than 0
and
no greater than the number of days in the current month.
Optional: Take into account leap year!
Additional Problem 2:
Here is a data definition for a world that consists of two objects: a
rock and a bird. The rock drops at a constant speed of 5 pixels per
tick; the bird flies horizontally at the same rate:
(define-struct world (bird rock))
;; A World is
;; --- (make-world Number Number)
;; Interpretation:
;; The first number is the x coordinate of the bird;
;; the second number is the y coordinate of the rock.
Develop the function world-next
, which creates the next world
from a given world.
Develop the function world-draw
, which creates a 200 x 200
scene with empty-scence
and place-image
from
the world. Create a first example by hand and use it to test the
program. Assume that the bird is always 120 pixels above ground level,
and that the rock is always 80 pixels from the left.
After the program is fully developed, use the world.ss teachpack to run
it like this:
(define (world-next w) ...)
(define (world-draw w) ...)
;; tests:
;; --- run program run:
;; World -> World
;; run for every tick of the clock
;; display the given world on the canvas
;; and produce the next world
(define (tock w)
(update (world-draw w) produce (world-next w)))
(big-bang 200 200 .1 (make-world 1 1))
(on-tick-event tock)
Additional Problem 3:
Develop a program that draws a colored rectangle frame around a small
image that occurs in a larger one. If the smaller image does not occur
inside the larger one, the program just returns the larger image as is.
Hint: Study the documentation for image.ss
in the DrScheme
help desk, especially the
functions image-inside?
, overlay/xy
,
and find-image
. Note that overlaying one picture on another
puts the images on top of each other at an imaginary, centered pin-hole.
(If you like body piercing, think of this as picture piercing, right
smack in the middle.)
Optional:
Please explain any problems you had completing this assignment in no more than 30 words.