CSC151 2007S, Class 46: Merge Sort

Admin:
* Notes on HW13
* Due: HW 15
* Assigned: HW 16
* Exam 3 distributed Friday
* Sam will figure out something reasonable with HW grading so that the
  GIMP grades don't too adversely affect your final grade.
* EC for supporting the softball team
  * Wednesday at 3ish and 5ish
  * Thursday at similar times
  * Saturday at similar times
  * Sunday at similar times
  * Yay snow/raindates!
* EC for Thursday's convo on lying
  * Don't lie about going

Overview:
* Key Ideas.
* Lab.
* Reflection.

/Merge Sort: Key Ideas/

* Sort things by dividing them in half, sorting each half, and then ...

/Reflection/

Comparing two names:

The long way

(define name-precedes?
  (lambda (name1 name2)
    (if (string-ci<=? (car name1) (car name2)) 
        #t
        (if (string-ci<=? (car name2) (car name1))
            #f
            (if (string-ci<=? (cadr name1) (cadr name2))
                #t
                #f)))))

(define name-precedes?
  (lambda (name1 name2)
    (if (string-ci<= (car name1) (car name2))
        #t
        (if (and (string-ci=? (car name1) (car name2))
                 (string-ci<=? (cadr name1) (cadr name2)))
            #t
            #f))))

(define name-precedes?
  (lambda (name1 name2)
    (or (string-ci<= (car name1) (car name2))
        (and (string-ci=? (car name1) (car name2))
             (string-ci<=? (cadr name1) (cadr name2))))))