Processing: Creative Coding and Computational Art

The items array has 50 places reserved in memory for ints. The itemNames array has
10,000 places reserved in memory for Strings, and the obs array has 0 spaces in memory
for Objects. In general, you wouldn’t initialize an array with 0 items, but you could. Finally,
there is one additional way to initialize an array, when you know ahead of time what will
be in it:
int[] speeds = {2, 4, 445, -120, 3, 90, 54};
This array will have a length of 7, and, like all arrays, its size can’t be changed. Here’s
another example with a String array:
String[] names = {"Lulu", "Ivan", "Myrna", "Pookie"};
So, once you declare and initialize arrays, how do you use them? An index system is used
to access the values (called elements) stored at the different positions in the array. It’s a
very simple system with one caveat: arrays are zero-indexed, which means the first position
in the array is at position 0, not 1. There are some benefits to this, which you’ll see
shortly when we get to for loops, but in the beginning it can be confusing.
Going back to the previous array, int[]speeds = {2, 4, 445, -120, 3, 90, 54}, to
access the first item—the value 2—I use speeds[0]; to access the third item, 445, I use
speeds[2]; and for the last item, 54, I use speeds[6]. Make sure you understand this
before you move on; it’s important. Arrays also have a built-in length property that you’ll
use often. You access the property with dot syntax. To find the length of the speeds array,
you write speeds.length.
The length of the array is the actual number of items in the array, so speeds.length is
equal to 7, even though speeds[6] gives you the last item in the array. You should see how
working with arrays is both simple and a little complicated.
Finally, if you try to access an index that is out of range—for example, if you try to access
speeds[7], which doesn’t exist—you’ll get a compiler error. This may seem like a pain, but
again it’s there to help you.
Loops
One of the best uses for computers is handling repetitive, redundant tasks that are too
tedious for most people. This is accomplished in programming by using structures called
loops. Loops are structures that continue to run, or execute, until some condition is met
that causes them to stop. The two types of loops listed in the Processing language reference
are while loops and for loops. In addition, we’ll look at one other variation on the
while loop called a do...while loop.
while
Here’s an example of a while loop, (which I don’t recommend you run):
while (true) {
println ("help I'm in an infinite loop");
}
CODE GRAMMAR 101
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