CSC151 2010S, Class 04: An Introduction to Scheme

Overview:
* Why use programming languages?
* Scheme basics.
* Scheme history.
* Lab.

Admin:
* Reading for Monday: 
  Programming the GIMP Tools.
* Assignment for Wednesday: 
  Algorithms for Drawing.
* Quiz 1 released.  
  Email me an answer by midnight tonight.
* The joy of ambiguity: 
  Suppose someone doesn't fill in the course number on an add/drop form
  Writes in section 01
  Has me sign it
  What should happen?
* I'm working on responses to assignment 1.  
  I hope to have them done this evening.

About Programming Languages:
* Computer scientists like to design languages
  in which to express algorithms.
* Why?
  * The feeling of superiority one has when it
    can use jargon that no one else understands
  * A design language can be more concise
  * Lack of ambiguity
  * Easier to "parse"
  * Two important characteristics to each compuetr language:
    * The "syntax" - HOW you say things
    * The "semantics" - WHAT those things mean
  * Time flies like an arrow
  * Fruit flies like a banana

About Scheme:
* Designed at MIT as a teaching language
* Really simple syntax
* Supports multiple models of algorithm design
* Basic activity: Apply a defined routine to 
  some values
(OPERATION VALUE VALUE VALUE)
(+ 1 2 3)
(* (+ 1 2) 3)
* Basic activity: Naming values
(define NAME value)
(define PI 3)
(* 2 PI)
(define add +)
(add 2 3)
(add                                 2


3)

Lab/Reflection
* Nora says: "Be sure to trade off who is at the
  keyboard."
* Sam says: How did you confirm your sqrt answer?