CSC151 2010S, Class 34: Geometric "Art" Through Numeric Recursion

Overview:
* Questions (Numeric Recursion; Geometric "Art"; Life, the Universe, and Everything)
* Unclear Answers
* Lab

Admin:
* Reading for tomorrow: Characters and Strings.
* We may have prospectives on Friday.  Fun fun fun!  (If you object to using class time to annoy prospies, we can skip the fun.)
* Three stories about The Advisee (if you want them).
* EC for Today's CS and Disability talk (4:30 in Science 3821).
* EC for Wednesday's CS and Disability talk (4:15 in JRC101).
* EC for Thursday's convocation.
* EC for Thursday's "Teaching Millenials" CS Extra (4:30 in Science 3821).
* EC for Friday's "Computational Games" CS Extra (noon in Science 3821; Free Pizza; I'll need an approximate count on Wednesday).
* I will strive to make the rest of today a "Sam just answers questions" day.

;;; Procedure:
;;;   cname->rgb-list
;;; Parameters:
;;;   cname, a color name
;;; Purpose:
;;;   Determine the components of the RGB color that
;;;   corresponds to cname.
;;; Produces:
;;;   components, a list of three integers, each in the
;;;     range 0-255.
;;; Preconditions:
;;;   cname must be a valid color name, that is
;;;     (color-name? cname) is #t
;;; Postconditions:
;;;   components is a list of three integers, (r g b)
;;;      0 <= r < 256
;;;      0 <= g < 256
;;;      0 <= b < 256
;;;   (rgb->color-name (rgb-new r g b)) = cname
(define cname->rgb-list 
  (o rgb->rgb-list color-name->rgb)) 

;;; Procedure:
;;;   c
;;; Parameters:
;;;   cnames, a list of color names
;;; Purpose:
;;;   Count colors with dominant components
;;; Produces:
;;;   stuff, a list of four numbers, (x y z q)
;;; Preconditions:
;;;   
;;; Postconditions:
;;;   x is the number of colors in cnames in which red dominates
;;;   y is the number of colors in cnames in which green dominates
;;;   z is the number of colors in cnames in which blue dominates
;;;   q is the number of colors in cnames in which no color dominates

(define count-dominant-components
  (lambda (cnames) 
    (if (null? cnames) 
        (cons 0 (cons 0 (cons 0 (cons 0 null))))
        (let* ((x (count-dominant-components (cdr cnames))) ; x is a list of four integers
               (components (cname->rgb-list (car cnames)))
               (red (car components))
               (green (cadr components))
               (blue (caddr components))
               (r (car x))
               (g (cadr x))
               (b (caddr x))
               (z (cadddr x)))
          ; if the red component of the first value is the
          ; largest of the three components
          (cond
            ((> red (max green blue))
             ; Add one to the first element of x
             (list (+ 1 r) g b z))
            ; if green is the largest of the three components
            ((> green (max red blue))
             (list r (+ 1 g) b z)) 
            ((and (> blue red) (> blue green)) 
             (list r g (+ 1 b) z))
             ; If at least two components are the same
            (else
             (list r g b (+ 1 z))))))))