Flash MX 2004 Games : Art to ActionScript

Flash MX 2004 Games
Computationally this uses much less processing power, for no loss of accuracy. Always look
out for times when you can lower the hit on the processor because your games will play more
smoothly.
It doesn’t seem very logical to me!
We’ve looked at how we can use the ‘if ’ statement to select which code to run. So far we have
used a single condition. But we can combine conditions using either an ‘And’ operation or an
‘Or’ operation. Flash uses the symbol ‘&&’ to represent And, and the symbol ‘||’ to represent Or.
So how do we use these to combine conditions? The ‘And’ option means that all the conditions
must be true for the combined condition to evaluate to true. The ‘Or’ option just requires a
single condition to evaluate to true for the combined result to evaluate to true. Truth tables are
often used to show the results of combinations; Table 8.2 gives the truth tables for both ‘And’
and ‘Or’.
Let’s look at how we can use these options to improve our
conditional statements. Suppose we want to run a section of
code if our character is inside a rectangle on screen. We will
Table 8.2 And and Or truth
define the rectangle using the upper left corner and the lower
tables �
��� �
And
��
true false
right corner. To be within the region the character’s _x pos-
true
��
��
�
ition must be greater than the value for left of the rectangle
true false
false ��
� false false
and also less than the value for right, in addition the character’s
�
��
Or ��
true false
_y position must be greater than the top line of the rectangle
��
true ��
��
� true true
but less than the bottom line. So how do we put this into
false �
�
� true false
code? Let’s consider the rectangle (100, 200, 300, 400). Here
the left side is at 100, the top is at 200, the right is at 300
and the bottom is at 400. If we have a movie clip called clip then the code we would use
would be:
if (clip._x>100 && clip._y>200 && clip._xtop && x