CSC151 2007S, Class 08: Procedure Definitions

Admin:
* Due: HW 4
* Reading for Monday: Boolean values and Predicate procedures.
* Yes, there's a new homework for Tuesday: Mad Libs.

Overview:
* Why define your own procedures?
* How to define your own procedures.
* Lab.

/What/
* A procedure is a chunk of code
  * That has a name
  * That may have parameters
  * The chunk is often called the "body"

/Why/
* Their instructor tells them to
* Clarifies the program
  (+ (- b) (sqrt (- (sqr b) (* 4 a c))))
  vs.
  (quadratic-root a b c)
* Shortens the program when you do the same thign over and over again
* Lets you (or someone else) figure out a solution, and then lets
  others use the solution
  * Permits you to focus (elsewhere) on the *what* not the *how*

/How/
(define NAME
  (lambda (PARAMS)
    BODY))
(define increment
  (lambda (x)
    (+ x 1)))

/Lab/

* 3c is a thought question
* Do not document, unless told specifically to do so.