0. #lang htdp/bsl
1. (require 2htdp/image)
2.  
3. ;; dist : Number Number Number -> Number
4. ;; Returns the distance from the origin (0, 0, 0) to the point (x, y, z)
5. (define (dist x y z)
6.   (sqrt (+ (expt x 2) (+ (expt x 2)
7.                          (expt y 2)))))
8.  
9. ;; iff : Boolean Boolean -> Boolean
10. ;; Returns #true if sunny is #true and beach is #true,
11. ;; or sunny is #false and beach is #false, else returns #false
12. (define (iff sunny beach)
13.   (cond [(and sunny beach) #true]
14.         [(and (not sunny) (not beach)) #true]
15.         [else #false]))
16.  
17. ;; compute-width2height-ratio : Image -> Number
18. ;; Returns the width-to-height ratio of the given image
19. (define (compute-width2height-ratio img)
20.   (/ (image-width img) (image-height img)))
21.  
22. ;; image-classify : Image -> String
23. ;; Classifies an image into one of 5 categories based off of its width-to-height ratio
24. (define (image-classify img)
25.   (cond [(> 1 (compute-width2height-ratio img)) "portrait"]
26.         [(= 1 (compute-width2height-ratio img)) "square"]
27.         [(>= 4/3 (compute-width2height-ratio img)) "fullscreen"]
28.         [(>= 16/9 (compute-width2height-ratio img)) "widescreen"]
29.         [else "too wide"]))
30.  
31. ;; image-area : Image -> Number
32. ;; Returns the number of pixels found in a given image
33. (define (image-area img)
34.   (* (image-width img) (image-height img)))
35.  
36. (define shape1 (rectangle 20 40 "solid" "black")) ;; should be < 1:1
37. (define shape2 (rectangle 40 40 "solid" "red")) ;; should be 1:1
38. (define shape3 (rectangle 40 30 "solid" "yellow")) ;; should be 4:3
39. (define shape4 (rectangle 71 40 "solid" "green")) ;; should be ~16:9
40. (define shape5 (rectangle 100 40 "solid" "blue")) ;; should be > 16:9
41.  
42. (check-within (dist 10 10 10) 17.321 0.001)
43. (check-within (dist 5 7 20) 21.772 0.001)
44. (check-within (dist 3 4 5) 7.071 0.001)
45.  
46. (check-expect (iff #t #t) #t)
47. (check-expect (iff #t #f) #f)
48. (check-expect (iff #f #t) #f)
49. (check-expect (iff #f #f) #t)
50.  
51. (check-expect (image-classify shape1) "portrait")
52. (check-expect (image-classify shape2) "square")
53. (check-expect (image-classify shape3) "fullscreen")
54. (check-expect (image-classify shape4) "widescreen")
55. (check-expect (image-classify shape5) "too wide")
56.  
57. (check-expect (image-area shape1) 800)
58. (check-expect (image-area shape2) 1600)
59. (check-expect (image-area shape3) 1200)
60. (check-expect (image-area shape4) 2840)
61. (check-expect (image-area shape5) 4000)

=>

Ran 17 tests.                                                                                    2 of the 17 tests failed.                                                                        Check failures:                                                                                                       ┌─────────────────┐                                        ┌──────────┐             Actual value │ 9.9498743710662 │ is not within 1/1000 of expected value │ 5443/250 │.                         └─────────────────┘                                        └──────────┘     at line (unknown), column (unknown)                                                                                   ┌───────────────────┐                                        ┌───────────┐         Actual value │ 5.830951894845301 │ is not within 1/1000 of expected value │ 7071/1000 │.                      └───────────────────┘                                        └───────────┘ at line (unknown), column (unknown)                                                              Ran 17 tests.                                                                                    2 of the 17 tests failed.                                                                        Check failures:                                                                                                       ┌─────────────────┐                                        ┌──────────┐             Actual value │ 9.9498743710662 │ is not within 1/1000 of expected value │ 5443/250 │.                         └─────────────────┘                                        └──────────┘     at line (unknown), column (unknown)                                                                                   ┌───────────────────┐                                        ┌───────────┐         Actual value │ 5.830951894845301 │ is not within 1/1000 of expected value │ 7071/1000 │.                      └───────────────────┘                                        └───────────┘ at line (unknown), column (unknown)