CS99 Lecture 3
- week of 9/4

Intro
- computer languages all have a philosophy
- MATLAB (arrays), Java (objects), Maple (symbolics)
- knowing philosophy means knowing how to make most of the language

Languages
- written vs spoken
- written has syntax (grammar) and semantics (meaning)
- writing an instruction is like writing a sentence

Langauge-Elements for Maple
- characters (0123456789abcdefg etc)
- tokens (things built from characters (think "words"))
- token separators (blank spaces)
- escape character (characters that don't really form "sentences" -- they
  issue commands)
  (? "escapes" to help)

Tokens in Maple
- used to build command you enter into Maple
- things like equations
- types:
  operator
  name
  reserved word
  integer (yes, Maple has no real floats! -- floats are built from
           integers -- students probably won't care about this for now)
  punctuation
  string
- separate tokens with token separators (see above)

Why bother?
- look at many of these elements
- also in many other languages
- how they work in Maple is very sim to other languages

Looking at Operators...
- Arithmetic
  +*-/^
- (skip functional syntax)
- precedence (* before +)
- associativity (/ before -)
- need parentheses!

Looking at Names...
- purpose: need something to store values
  usually called variables, but formal name is...err...name
- symbols 
  rules: letters, numbers, underscore, not start with number
- name = symbol with property of indexing 
  (what's indexing? hmmm...save for later)
- protected names -- Maple predefines some names to be used for 
  "popular" things like functions (sin, cos, tan, sqrt, and more)
- backquote -- beasatly things
  can form weird looking names with backquotes (``)
  not to be confused with forward quotes ('')

Looking at Reserved Words...
- also called keywords
- most languages have them
- things that are intrinsic to the language
- cannot change meaning because language needs it!
  (imagine chaos if we really changed the definition of "is")

Looking at strings and integers....
- well, not really -- saving that for chapter 4

Statements
- each line of code of Maple is like a sentence
- Maple "sentences" called statements
- end sentences with periods
- Maple's statements end with semicolon and colon
  (semicolon - show output, colon - suppress output)
  (hard to demonstrate this until lab)