Expressing, combining, transforming values in
The video tutorials below are to help you learn how to express,
transform, combine, and decompose values in the DrRacket
programming environment. This is a lot more fun if you installh
DrRacket for your computer platform, and work through the examples.
In case videos aren't your preferred source for learning, I've
also included some other resources with each video.
express values video
Expresses bicycle, lizard, and giraffe images, the number
five, the character string "string", as well as truth and
lies. Once you're done with the video, you should be able
Represent images you copy inside the DrRacket
programming environment, flip them, and find out how
wide or tall they are
Represent exact numbers --- such as 5, 7, and 5/7
--- as well as inexact numbers, such as the square root
Represent strings, such as "counter-clockwise", and
find out how many characters they contain.
Represent true and false, and
toggle between them.
Here are some relevant non-video resources for this topic:
Guide for Racket's 2htdp/image
tools for manipulating
images. These tools are automatically
included if you (require picturing-programs).
On the same page you'll find lots of other tools
explained, including image-width and
Guide for Racket's Intermediate
Student with lambda on sqrt and other numeric
tools... Poke around enough and you'll also find stuff on
strings, true, and false as well.
transform values video
Finds images on the web, or your hard drive, and flips,
rotates, or scales them. Once you're done with the video,
you should be able to:
Flip an image left-to-right or top-to-bottom.
Rotate an image, say, 270 degrees
Scale an image so that it is twice, or half, as
Scale an image so that it is shorter, but wider,
than it was originally.
Non-video resources that are relevant to this topic:
1 and Chapter
3 of Stephen Bloch's Picturing Programs
gets you started on manipulating images and working in
Guide to Racket's 2htdp/image
tools, which are included when you (require
combine values video
Combines images, numbers, character strings, truth, or
lies, and produces new values from them. Once your done
with the video, try the following:
Place four images beside each other (it helps to
choose small ones).
Place images above others.
Create a solid red circle of size 15. What do you
figure the size number means?
Append three strings to produce "all together now"
(notice the spaces).
Multiply the integers from 1 through 10. Add the
same integers. What happens if you use the subtraction
operator? What about division?
What values does (< 2 3 5 7) produce? What about
(< 2 3 7 5)? Explain the results.