Game Development Reference
In-Depth Information
Nested Repeats
The body of a
while
instruction or a
for
instruction is an instruction. This instruction can be an
assignment, a method call, a block of instructions delimited by braces, or another
while
or
for
loop.
For example:
var x, y;
for (y=0; y<7; y++)
for (x=0; x<y; x++)
Canvas2D.drawImage(sprites.lives,
new Vector2(x * sprites.lives.width, y * sprites.lives.height));
In this fragment, the variable
y
counts from 0 to 7. For each of these values of
y
, the body is
executed, which consists of a
for
instruction. This second
for
instruction uses the counter
x
, which
has as an upper limit the value of
y
. Therefore, in each progression of the outer
for
instruction, the
inner
for
instruction goes on longer. The instruction that is repeated draws a yellow balloon sprite
at the position calculated by using the values of the
x
and
y
counters. The result of this loop is a
number of balloons placed in the shape of a triangle (see Figure
10-4
).
Figure 10-4.
Balloons in a triangle shape
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