CSC302 2011S, Class 19: Clojure (2)

Overview:
* Review of highlights
* Lab.

Admin:
* Assignment 7 almost released.  (Discussed in class.)
* We will skip day 3 of Clojure and move on to Haskell next week.
  * No need to read clojure-3.
* Wednesday: Growing a Language.  Friday: The Design of C++.

Big Points of Section N.3.
* Macros: 
  * Manipulates program TEXT rather than data
  * Effect: delays execution
* Recursion in Clojure
  * Need special syntactic sugar to get efficient tail recursion
  * Why can't Clojure do sensible tail recursion?  The claim is "It's the
    JVM", but that seems specious.
* Sequences
  * Can build lazy sequences: Only evaluated "when needed", possibly
    infinite
* "Object-oriented" - Protocols that you implement
  * Organized
  * Syntactic sugar for common "object" stuff.
  * Lets you interface with Java and Microstuff.
  * Gives you the wonder of "Lists and Maps and Sets are all sequences." 
  * Polymorphism done the right way
    "list cons does X"
    "vector cons does X"
    ...
    rather than
    (defn cons [thing]
      (cond
        ((list? thing) ...)
        ((vector? thing) ...)))