Details for Monday Morning

  A Computer Science should not be tolerated in high school; it should be
  a core course like English or Algebra.

  Why it isn't -- justifiedly
  How we can make it one -- the goals of TeachScheme!

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  PROGRAM is a mechanism that consumes some class of information and
  produces a class of information in response, "big" examples

  COMPUTATION is the process when a program consumes a particular piece of
  information, works with it, and produces some information in response

  INFORMATION: some knowledge about the "world"

  Small example:  
    - conversion of temperature
    - consumes degrees according to Celsius 
    - produces degrees according to Fahrenheit
    - when we apply it to 0C, we get 32F: that's a computation

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  PROGRAMMING LANGUAGE: a language for describing programs and, ideally, computations
  Algebra is such a language!

  DATA: a representation of information in the chosen computer language

  Questions: 

  COMPUTER: "Where is computer?" -- it doesn't matter!
  INPUT/OUTPUT: How do we get data into the computer? -- it doesn't matter

   --> picture

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  How do we calculate temperature conversion: algebra expression
    -- Scheme expression
  If we use it many times, we want to name the rule and learn to use it 
    -- Scheme definition, application 
  What does it all look like in DrScheme?

  area of disk: expression; Scheme + calculation
  area of ring (disk with hole): expression; Scheme  + calculation

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  THE RECIPE

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  Here are the "rules" (programs) to convert
    -- inches to cm   (define (inches-to-cm i) (* 2.5 i))
    -- feet to inches (define (feet-to-inches f) (* 12 i))
    -- feet to cm     (define (feet-to-cm1 f) 
                        (* 30 i))
                      (define (feet-to-cm2 f) 
		        (inches-to-cm
		          (feet-to-inches f)))
  The last two are equivalent; the second one is far better: when I
  introduce a better conversion, I only change one function. 

  They are equivalent by function composition, an algebraic concept w/o
  motivation that has just become extremely useful. Point to table in book
  with 12 conversion functions. 

  THE FIRST PRINCIPLE: re-use functions! 
  

RECAP:      area of square

PRAGMATICS: some syntax errors, some run-time errors

ASSIGNMENTS: 
 
 - 2.4:1; 2.5:1+2

 - 2.10; 2.11

 - 2.14

PLAY: ping-pong, use ping-pong-lib.ss (change-speed)