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Index › Programming Questions & Help › Syntax Questions › beginner questions
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beginner questions (Read 602 times)
aspy591
beginner questions
Apr 22nd, 2006, 1:32pm  
Hi, I am new to processing and programming in general. My only previous experience is with the functional programming language Haskell.

Ive figured out enough to create a ball that bounces around the window, and that accelerates toward the cursor upon mouse-click. Lets say I wanted to make the right mouse button create a new ball. The only way I can currently conceive to do this is to keep a list of particle positions, x velocities, and y velocities, and add to this upon right mouse click.

But there must be a less clumsy way to do it. Can functions actually create new global variables? As far as I know any variables declared within a function are only accessible to tha function.
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JohnG
Re: beginner questions
Reply #1 - Apr 22nd, 2006, 2:07pm  
If you use arrays, you can either just add a new pair of positions/velocities to an existing array, or you could look into creating a class for your ball, and just add a new ball to an array of balls.
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aspy591
Re: beginner questions
Reply #2 - Apr 24th, 2006, 3:17pm  
classes..reading the tutorial linked in the 'class' entry of 'Reference', and looking at some Processing examples..I think I pretty much get them. Just have to code up some experiments now. How do I destroy an object? Say a ball moves, and eventually exits the window. I dont like the idea of a bunch of invisible balls accumulating in memory.
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JohnG
Re: beginner questions
Reply #3 - Apr 24th, 2006, 4:05pm  
You can't manually delete anything, but it'll happen automaticly.

If you remove the reference to it in the array, e.g. make the array shorter, assign a new ball to that part of it, or set it to null, then the ball will get cleand up by Java's garbage collector.
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aspy591
Re: beginner questions
Reply #4 - Apr 27th, 2006, 2:22pm  
hi again, thanks for the replies.
Another question: Is it possible to make a function return two values of different types, eg a float and an array of ints?
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fry
Re: beginner questions
Reply #5 - Apr 27th, 2006, 3:01pm  
not really in any efficient way.. but if it's a float and array of ints, then you can return the float, and pass in an array to be set by the function and that'll work:

Code:
public float myfunction(int[] outgoing) {
  for (int i = 0; i < outgoing.length; i++) {
    outgoing[i] = 45;
  }
  return 45.2;
}


note that you'll have to create the "outgoing" array beforehand.
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