CSC195, Class 36: Reading Gries

Overview:
* Why discuss this issue?
* Background: How do you approach Gries?
* A basic technique.
* Exercise.
* Discussion.
* Other techniques.

Notes:
* Class next Friday (a week from today) in Saint's Rest.

Observation:
* Students read Gries
* Students don't seem to understand much

Coincidence:
* Kathleen Skerrett talked about how she teaches her
  students to read
* The miscegination of text and images

Detour: How do you read Gries?
* Lindsey: Read paragraph n again and again until perfectly
  understood.  Go on to paragraph n+1.
* Reese: Rough read and then read again.
* Erik: Read on until thoroughly confused.  Recover.
* Sam: Preread of pretty pictures and boldface words
  then read through.
  + What's the structure
  + What should I teach?
  + What are the hard bits that the students may need extra
    help with?

Skerrett suggests:
* In order to read a text, you must understand its topography
  + Look for outcroppings
  + Stay away from murky pools
  + Add signposts as you go
* Spend ten minutes generating a "map" of the text
  + It's worth that much time
* Using that map, go back and read the text
  + Read the text with a question
  + Read the text with a social purpose

What, if anything, did you learn from our mapping?
What do your maps look like?
* Extended outlines
  + A few bullet points under each
  + Expected importance -> time to spend
* Marked important things
* Marked confusing things
* Separate "definitions and theorems" section

What's important?
* Syntax and informal semantics of loop command
* Use of invariants to prove things
* Preconditions
* Formal definition of the do is important
  + Gries follows it up with a pithy comment
* Proof of loop correctness

Interesting:
* Note of similarities between do and if
  [Clear already after quick glance.]
* Multiplication procedure is interesting
  [Do you need to understand it?]

Murky:
* About four pages developing theorem on p. 144 and

Observation:
* There's more to the examples than examples.
* Structure of the book is important
  + Chapters 1-6 (approximate) background materials
  + Chapters 7-14 (approximate) formal definitions of
    programs
  + The rest: The payoff
Irritation:
* Too much foreshadowing: "You're learning this boring
  garbage for a good reason that you'll learn later."