For 0.5

To write list answers, give the first three items, then ... to the last item. The long list:

(list 21 22 23 24 25 26 27 28 29 30)

should be written:

(list 21 22 23 ... 30)

Range

Instructions

This section contains a mix of “stream-making” commands like in-range and lists. When the question gives a stream making command, write the list it will produce. When the question gives a list, write a stream-making command that could be used to produce it.

Short Exercises

• (in-range 30)
• (in-range 5 28)
• (in-range 5 28 10)
• (list 0 1 2 3)
• (list 80 81 82 83 84 85 86 87)
• (list 70 77 84 91 98 105)
• (list 16 15 14 13 12 11 10 9)
• ([y (in-range 30)] #:when (zero? (remainder y 8)))

Full Example, Explained

In the code below:

1. y runs through the integers 0, 1, … 29;
2. it contributes to the answer when the remainder of y divided by 8 is zero — that is, y is a multiple of 8; and
3. each of these y values produces an outline black triangle in the final list.

(for/list ([y (in-range 30)]
           #:when (zero? (remainder y 8)))
  (triangle (+ y 20) "outline" "black"))

Complete Exercises

1. As part of making a simple graphing calculator app, you need a list of posns (x,x^2) as x goes from -10 through 10. Write code to make that list.

2. Given the definition:

    (define WO (list "red" "green" "blue"))
   

   produce the list

    (list "Color is red" "Color is green" "Color is blue")
   

3. Given the definitions:

    (define ALPHA "abcdefghijklmnop")
    (define NS (list 2 0 11 5))
   

   Produce a list where the number n from NS gives the letter at index N in ALPHA, so (list "c" "a" "l" "f") in this case.

4. Given the definition:

    (define PN (list pic:hacker pic:book
                     pic:calendar pic:bloch))
   

   Create a list where each image has a 25 pixel high solid light blue rectangle underneath it. The width of the rectangle should match the width of the image.