Today in 151: About Scheme

Overview
* Introduction to Scheme
* Short history of Scheme
* Lab
* Possibly: Reflection
  + Hardest part today?
  + Something interesting you learned

Administivia
* Experiment today: Computer as whiteboard
  + Preserves what I write (legibly!)
  + No pictures
* Note on "proper" HTML
* Questions on homework 1?
* Sam will teach cool style stuff on Monday
* Other administrative questions?
* Homework: Don't bother to read "Lists" and "Symbolic Values"
* Sam is a broken record: Surveys to be read over the weekend
* Have a good weekend

Question: Tell us about the different kinds of links in HTML.
* "General": To a page somewhere else on the World Wide Web
  Such links always start with "the protocol"
  http:/
  https:
  ftp:
  mailto:

  <a href="http://www.grinnell.edu">The best darn liberal arts
  college in Grinnell</a>
* "Relative": Elsewhere in your account.  Simply give the
  name of the file
  <a href="cooka.html">My favorite person to pick on in this
  semester's version of CS151</a>
* "Internal": Within a page
  Precede the name of the part of the page with a pound sign
  
Question: What do you call the thing in a tag that give
extra info, like

<a href="#whatever">

Answer: You call it an "attribute"

Question: How do I find out all the thousands of different
parameters I can use?

Answer: Go to 
  http://www.w3.org/TR/html4/

Question: What do you want for citations.

Author.  Date.  Title.  URL if a Web page.  

Stone, John David and McRitchie (2003).  The Grinnell College
Department of Mathematics and Computer Science Front Door.
Web page available at http://www.cs.grinnell.edu/.  Visited
24 January 2003.  Last modified 22 January 2003.

About Scheme:
* Scheme is a programming language
* It is a language in which you express algorithms in a way
  that the computer can understand.
* It is designed to be simple and easy to learn compared
  to other programming languages.
* Simple syntax: Rules for forming "sentences"
* Here's the syntax
  Open parenthesis: (
  Operation: + 
  Arguments separated by spaces: 2 3
  Close parenthesis: )
* "Add two and three": (+ 2 3)
* "Find the square root of five: (sqrt 5)
* "Add two and three, multiply the result by 5"
  (* 5 (+ 2 3))
  (* (+ 2 3) 5)
  (5 * (+ 2 3)) NO NO NO
* Add two three and four
  (+ 2 3 4)
* Quadratic equation?

Where does Scheme come from and why do we use it at Grinnell?

In the late 1950's/early 1960's computers were used for ...
* Networking (not so much)
* Number crunching: Calculation
  + Accounting
  + Physics (big big calculations)
  + Statistics, Economics, and other numerical fields
  + Fun with missle trajectories and other military apps
* Encryption/Decryption
* Business data analysis

Movement: Artificial Intelligence:
* Goals: Understand and mimic human thought
* Theory: Thought is the manipulation of abstract symbols
  that are collected together.
* Need: Language that emphasizes symbols and collections
  of symbols.
* John McCarthy of MIT designed LISP (LISt Processing langauge)
* Early 1980's MIT revamps intro CS curriculm using LISP
 (okay, a variant): Scheme

Why Scheme at Grinnell
* Easy to learn/Simple syntax
* Puts everyone at an equal disadvantage
* Does some things easily that other languages don't
  (higher-order functions) (ignore for now)
* Encourages a program design technique known as recursion