CSC151 2007S, Class 04: An Introduction to Scheme

Admin:
* Sorry, my weekend got eaten by statistics.  Expect responses to assignment 
  1 later this week.
* Are there questions on assignment 2?  
  * If you work in a group, you should just turn in one assignment for 
    the group, with everyone's name at the top.
* Sleep lecture!  I don't like to see emails from you at 2 a.m.
  * If it's my homework that's keeping you up beyond midnight, send me
    email at midnight that says "Sleep trumps CS" and you get a free
    extension.
* Instructions for working at home likely to be ready early next week.
* Reading for tomorrow: GIMP tools

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

==Programming Languages==

* Formal mechanisms for expressing algorithms
  * For computers
  * For humans
* Ambiguity = Death
* Why not use natural language?
  * Ambiguous
  * Hard to parse
    * Time (subject/noun) flies (verb) like an arrow (adverbial phrase)
    * Fruit (adjective) flies (plural noun) like (verb) a banana (direct object)
* Tens of thousands of programming languages
  * Amazingly, differnt opinions on what makes a programming language good
  * Different features appropriate for different domains
  * Combining doesn't work
* We're using Scheme
  * A programming language with a lot of parentheses
  * Parentheses serve as a signal to the computer (and to the reader)a
    (SOMETHING ...) - Assumes that SOMETHING is a procedure, and attempts
    to apply it
    (+ 1 2 3)
    (sqrt 5)
    (1 + 2) - Whoops, 1 isn't a procedure BOOM
  * Designed as a teaching language at MIT
    * Simple
    * Not a lot of syntax
    * Not too many basic operations
    * But powerful
  * Based on Lisp, one of the first programming languages

== Work on Lab ==

== Some Reflections ==

* How did you know that the result is correct?