Date: Tuesday, 08 April 2008 12:33 PM 
   From: Mark Jacobson <jacobson@math-cs.cns.uni.edu>
     To: 810-088-09-spring@uni.edu
Subject:  Quiz tommorrow... Wednesday

Hi Flash students,

     Reminder: Quiz 5 will be tommorrow.  The study guide for quiz #5 will 
be the same study guide that was used for quiz #4.

     http://www.cs.uni.edu/~jacobson/flash/quiz4.txt

     Math.floor() and Math.random() are the two functions we reviewed
extensively yesterday when we went over quiz #4.

     Here is the code we used last Friday to make the racing rectangles:

    r1.x += Math.random() * 12;                <--- Version without using
    r2.x += Math.random() * 12;                        Array approach was
    r3.x += Math.random() * 12;                                done first.
    r4.x += Math.random() * 12;

     for (var i:int = 0; i < 4; i++) {          <--- Array version
         r[i].x += Math.random() * 21;                 was done last.
     }

     Note how both use Math.random() function and multiply by 12 or by 21.

     Of course, the 2nd version had to store the rectangle objects
in the array first with the following four statements.

r[0] = r1;
r[1] = r2;
r[2] = r3; 
r[3] = r4;
                                                    ------------
     What if we did the following instead: (Use the Math.floor() function).
                                                    ------------
     r1.x += Math.floor( Math.random() * 12 );

     for (var i:int = 0; i < 4; i++) {
         r[i].x += Math.floor( Math.random() * 21 );
     }

     http://www.uni.edu/jacobson/rectangleRace.html

     Using the Math.floor() function would cause no difference is how the
racing rectangles movie appeared to the user.

     Math.random() * 21 gives numbers like 1.593 and 19.2167 and 0.44821

     whereas

     Math.floor( Math.random() * 21 ) gives only these numbers:

               0, 1, 2, 3, 4, 5, ..., 18, 19, 20

     There are only 21 different outputs possible for

               Math.floor( Math.random() * 21 )

     whereas there are millions or billions of possible outputs for

               Math.random() * 21

                     i.e. 1.563127 and
                          1.563128 are different outputs or results.

                          1.0000001 is different from
                          1.0000002


     The take home quiz/assignment that was to be due tommorrow will be due 
on Friday instead of being due tommorrow.

     http://www.cs.uni.edu/~jacobson/flash

     Mark