Overview

• Preliminaries.
  • Admin.
  • Upcoming Work.
  • Extra Credit.
  • Questions.
• Numbers vs. Images.
• Testing.
• Lab.

Preliminaries

Admin

• New partners!
• Sam is incredibly behind on grading. Quizzes returned tomorrow. Exams may take another week.
• If you invoked "There's more to life", wait until you get your exam back to meet with me.
• We'll talk a little bit about testing.

Reminders

• Office hours: MTWF 10-11, Tu 1-2.
  • Sign up at http://rebelsky.youcanbook.me.
  • Also feel free to stop by when my door is open.
  • Or to email me for an appointment.
• Tutor hours
  • Sunday, 3-5 p.m.
  • Sunday-Thursday, 7-10 p.m.
• Weekly review sessions:
  • Wednesday at 8pm in the CS Commons with #Sorry Sarah
  • Thursday at 10am in this room with #Sorrier SamR
  • Thursday at 8pm in the CS Commons with #Apologetic Alex

Upcoming Work:

• Reading for Tuesday
  • Conditionals
• Assignment 4 due Tuesday night at 10:30 p.m.
• Lab Writeup: Exercise 1c.
  • Send email titled CSC 151 Lab Writeup 17 (Your Names)
  • Do not include the underscores.
  • Send to CSC151-02-grader@grinnell.edu
  • Due before class on Wednesday.

Extra Credit

• Send your reports to rebelsky@grinnell.edu with subject "CSC 151 Extra Credit".
• Send opportunities to me before class with subject "CSC 151 EXTRA CREDIT OPPORTUNITY!"

Academic

• Sexual Assault Awareness Week Discussion, Monday, 7:30 pm JRC 101
• CS Table, Noon, Tuesday, White PDR.
• State of SHACS Discussion, Tuesday, 7pm JRC 209
• Town Hall, Wednesday, noon or 7:30 pm (I think) JRC 101

Peer

• Pun Club Tournament Friday the 26th in the evening (Bobs).
• Contra Dance Friday the 26th in the evening (Main).
• Improv Show the 27th in the evening in Loose Lounge (7:30).
• Vote for SGA positions.
• Go to Wednesday's SGA meeting to make noise about the reserve.
• AppDev Pub Night, Friday, 8pm, Lyle's (JRC Basement).
• Black History Month Showcase, Friday, Harris, 7:30 p.m.

Regular Peer

• Social Dance Workshop Tuesdays 7:00-8:00 in Bucksbaum Dance Studio
• Pun club Saturdays at 4pm in Younker (max 2)
• Electronic Potpourri on KDIC Fridays at Five (TONIGHT)
• Space Odyssey KDIC Fridays at Six

No Extra Credit, But Still Good

Questions

Numbers vs. Images

• Images are misleading.
• Numbers are telling.

Testing

We'll work on some simple tests for smaller-neighbor.

• Goal of smaller neighbor: Make a copy of the same drawing, right next to it, but smaller.
• "Right next to each other" = "The borders are touching" = "The right of the orignal = the left of the neighbor" = (drawing-right original) = (drawing-left neighbor).
• Same shape.
• Same color.
• Proportionally smaller width and height (3/4 as big)
• Top should be the same

As a procedure.

(define check-right-neighbor
  (lambda (drawing neighbor)
    (check-= (drawing-right drawing)
             (drawing-left neighbor)
             .00001
             "next to each other")
    (check-= (drawing-top drawing)
             (drawing-top neighbor)
             .00001
             "tops aligned")
    (check-equal? (drawing-color drawing)
                  (drawing-color neighbor)
                  "same colors")
    (check-equal? (drawing-type drawing)
                  (drawing-type neighbor)
                  "same shape")
    (check-= (* 3/4 (drawing-width drawing))
             (drawing-width neighbor)
             .00001
             "proportional width")
    (check-= (* 3/4 (drawing-height drawing))
             (drawing-height neighbor)
             .00001
             "proportional height")))

Here's what we saw (more or less).

Welcome to DrRacket, version 6.1 [3m].
Language: racket [custom]; memory limit: 128 MB.
; Manually build a rectangle and its neighbor
> (define rect1 (rectangle "red" 50 30 20 20))
> (define rect2 (rectangle "red" 65 30 15 15))
> (check-right-neighbor rect1 rect2)
--------------------
FAILURE
name:       check-=
location:   (#<path:/home/rebelsky/Desktop/class17.rkt> 109 4 3110 124)
expression: (check-= (drawing-right drawing) (drawing-left neighbor) 1e-05)
params:     (70 65 1e-05)
message:    "next to each other"

. . Check failure
--------------------
; Okay, the left edge of rect2 was in the wrong place.  Fix it.
> (define rect2 (rectangle "red" 70 30 15 15))
> (check-right-neighbor rect1 rect2)
; Now we get no errors.  What happens if we recolor?
> (define rect2 (rectangle "grey" 70 30 15 15))
> (check-right-neighbor rect1 rect2)
--------------------
FAILURE
actual:     16711680
expected:   8421504
name:       check-equal?
location:   (#<path:/home/rebelsky/Desktop/class17.rkt> 117 4 3359 113)
expression: (check-equal? (drawing-color drawing) (drawing-color neighbor))
message:    "same colors"

. . Check failure
--------------------
; As expected, it tells us that the colors are not the same.
; Let's check the wrong shape.
> (define rect2 (ellipse "red" 70 30 15 15))
> (check-right-neighbor rect1 rect2)
--------------------
FAILURE
actual:     rectangle
expected:   ellipse
name:       check-equal?
location:   (#<path:/home/rebelsky/Desktop/class17.rkt> 120 4 3477 110)
expression: (check-equal? (drawing-type drawing) (drawing-type neighbor))
message:    "same shape"

. . Check failure
--------------------
; Now, let's see whether our smaller-neighbor procedure works.
> (check-right-neighbor rect1 (smaller-neighbor rect1))
--------------------
FAILURE
name:       check-=
location:   (#<path:/home/rebelsky/Desktop/class17.rkt> 109 4 3110 124)
expression: (check-= (drawing-right drawing) (drawing-left neighbor) 1e-05)
params:     (70 115/2 1e-05)
message:    "next to each other"

. . Check failure
--------------------
--------------------
FAILURE
name:       check-=
location:   (#<path:/home/rebelsky/Desktop/class17.rkt> 113 4 3239 115)
expression: (check-= (drawing-top drawing) (drawing-top neighbor) 1e-05)
params:     (30 45/2 1e-05)
message:    "tops aligned"

. . Check failure
--------------------
; Two failures!  The right and left edges don't match (way off) and
; the tops don't match (also off).

Lab

Writeup: 1c.