Processing: Creative Coding and Computational Art

PROCESSING: CREATIVE CODING AND COMPUTATIONAL ART
102
int[] getXYMotion(){
xpos+=xspeed;
ypos+=yspeed;
int[]xypos = new int[]{xpos, ypos};
return xypos;
}
The function return type is now an int[] array, not a primitive int. The function creates
an xypos array each time it’s called, and then returns the array. The other important aspect
to this approach is knowing how to receive the array that’s passed back. When I was originally
just returning an int back, it was simple, because it was the only value returned. But
to really benefit from this approach, the rect() call needs to be changed from:
to
rect(getXMotion(), ypos, 10, 10);
rect(getXYMotion()[0], getXYMotion()[1], 10, 10);
Does this make sense? I know it looks pretty strange. Remember, arrays are indexed,
beginning at [0]. When the array is passed back, it’s being received as a multivalue structure,
with xpos at the 0 index and ypos at the 1 index. These values are retrieved using
getXYMotion()[0] and getXYMotion()[1], respectively. If this is still not making sense,
imagine replacing getXYMotion() with the array. To get the value in the first position of
the array, you’d use arrayname[0]. To get the value in the second position, you’d use
arrayname[1]. I hope that helps. You’ll be doing stuff like this in future chapters, so try not
to freak out if this stuff is hurting your head—it’s supposed to in the beginning.
The last thing I want to say about functions relates to a nasty habit many coders get into.
Now don’t get any wrong ideas here. I’m talking about the use of magic numbers—what
were you thinking of? Magic numbers are values we hard-code into a program that make
the program difficult to change or customize. Using magic numbers is generally not the
way to develop a modular system, but it can be a fast way of hacking out a solution without
thinking of the big picture. In general, you’ll want to avoid them. Following are two
simple examples—the first using magic numbers:
//sketch using magic numbers:
size(200, 200);
background(255);
strokeWeight(5);
stroke(20);
fill(100);
rect (50, 50, 100, 100);
The second example improves upon this sketch, using a parameterized function instead of
the hard-coded values:
// sketch using a nice parameterized function
void setup(){
size(200, 200);
background(255);