Learn to Program with Small Basic

To move the square, we call the Move() method of the Shapes object
(line 8). This method takes three arguments: the identifier of the shape we
want to move and the x- and y-coordinates of the position we’re moving it
to. The squares in each row have their x positions (left edge) at 1 × 20 = 20,
2 × 20 = 40, 3 × 20 = 60, and so on. The squares in each column have their
y positions (top edge) at 1 × 20 = 20, 2 × 20 = 40, 3 × 20 = 60, and so on.
This is why we use c * 20 and r * 20 in the call to Move().
At the end of this For loop, the box matrix contains 32 unique identifiers
for the 32 squares created by the Shapes object.
The program then animates the squares (lines 13–18), using a nested
For loop to access the rows and the columns of box. During each iteration,
we ask the Shapes object to animate one square (line 15) and then pause for a
short time (line 16). The Animate() method takes four arguments: the identifier
of the shape we want to animate, the x- and y-coordinates of the destination,
and the animation duration in milliseconds. We ask the Shapes object to
move each square to point (0, 0) in 1 second (1000 milliseconds).
TRY IT OUT 17-2
Change the program in Listing 17-2 to animate the squares by columns instead of
by rows. If you’re feeling artistic, try moving the squares to create a pattern in the
graphics window.
Using String Indices
The previous examples used integer indices to access the elements of a
matrix. Our next example teaches you how use strings for indices. You’ll
examine an application that keeps track of students’ scores in different
subjects.
Welcome to Professor Xavier’s School for Gifted Youngsters! The class
has only three students right now: Scott, Jean, and Logan (the others are
on an important mission). The school teaches only three subjects: math,
science, and combat. Let's write a program that prompts the user to enter
a student’s name and then displays the student’s average score. The complete
program is shown in Listing 17-3.
1 ' StudentAvg.sb
2 score["Scott"]["Math"] = 92
3 score["Scott"]["Science"] = 90
4 score["Scott"]["Combat"] = 87
5 score["Jean"]["Math"] = 85
6 score["Jean"]["Science"] = 82
7 score["Jean"]["Combat"] = 92
8 score["Logan"]["Math"] = 85
9 score["Logan"]["Science"] = 95
10 score["Logan"]["Combat"] = 99
11
246 Chapter 17