Processing: Creative Coding and Computational Art

PROCESSING: CREATIVE CODING AND COMPUTATIONAL ART
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Congratulations! OK, so maybe it wasn’t a huge improvement to “Hello World,” but you
got to make a pretty, blue circle. Let’s look at the program line by line.
/* and */ are block comment tags, used to comment out multiple lines of information so
that it is ignored by the compiler. // can be used to comment out a single line. It is typical
at the top of a program to put some info about what your program does, who created it,
the creation date, and any other special notes. This is not required, but most people put
something up there. In fact, some people put a lot of stuff up there, including specific
code usage rights. How much you include up there doesn’t really matter because it won’t
affect how your program functions. However, novellas, mission statements, and manifestos
should probably be put other places. Here are some more examples of comments:
// this is a valid comment
/* this is a valid comment */
/*
this is a valid comment
*/
// this
// is also
// a valid
// comment
After the comments, I skipped a line. This is called whitespace. Whitespace in Processing
and Java is disregarded, as it is in many other programming languages. You can put as much
whitespace as you like to help you visually organize your code. The next line in the program,
size(200, 200); is a function call (I spoke about functions in Chapter 2—functions
are reusable blocks of code that you call when you need them). You know this because of
the parentheses after the word size. As stated in Chapter 2, a function call . . . well . . .
calls a function—in this case, a function named size. The numbers within the parentheses
are called arguments—things that are passed to the function, which the function expects
to receive and makes use of. In this case, the numbers represent the width and height of
the sketch window. When more than one argument is passed to a function, as in
size(200, 200);, commas are used to separate the individual arguments. There is no limit
to the number of arguments you can pass to a function, as long as the function has the
same number of parameters to receive the arguments. In addition, they must be sent to
the function in the same order that the function expects to receive them. In the case of
the function calls in the Hello Earth example, the functions I called are all built into the
Processing language, and thus you can’t see the actual function definitions. I’ll be
discussing functions in much greater detail later on in this chapter. For now, let’s keep
moving.
At the end of the size(200, 200); call, you should notice a semicolon. Semicolons in
coding are like periods in normal human language. They let the compiler know where the
end of the statement is. A statement is simply a command to the program to do something.
In Processing, failure to include a semicolon results in a compiler error—an error