Processing 1.0 - Processing Discourse - understandig some code

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understandig some code (Read 700 times)

punchik

understandig some code
Aug 23^rd, 2009, 11:25am

Hello, im trying to understand some code i found, there are 2 new things ive never seen in processing . Can anybody explain me what does it does?

the first one is this:
Set dotsNearMouse = hashGrid.get(new PVector(mouseX,mouseY));

what does set does? i why does the variable dotsNearMouse is not declared in the code?

and my last question is what does this means: for (Iterator i=dotsNearMouse.iterator(); i.hasNext() Wink

{}

?

here is the code:

http://www.soi.city.ac.uk/~jwo/processing/hashGrid/index.html

thanks

blindfish

Re: understandig some code
Reply #1 - Aug 23^rd, 2009, 12:03pm

I've never used Set, but the code seems fairly well documented on the page you linked to. From the linked documentation Set is clearly a class, so the line quoted is the declaration of dotsNearMouse...

iterator is a method of Set and seems fairly self-explanatory... Looks like it's needed in order to iterate through the contents of a Set, something like using a for loop to iterate over the contents of an array.

To be fair the styling on the site makes the links to documentation a little obscure, but they're there all right...

Where is the what if the what is in why?

antiplastik

Re: understandig some code
Reply #2 - Aug 23^rd, 2009, 1:38pm

Indeed, Set is a class. It's a Java Collection which, as the Javadoc states, contains no duplicate elements. For example : a set of cards.

Iterators are useful to... iterate through a collection. I won't go into details (see the link below) but for many reasons, you won't use this :
Code:

for (int i = 0; i < mySet.size(); i++) {
  myObject = mySet.get(i);
}

but this instead :
Code:

for (Iterator i = mySet.iterator(); i.hasNext(); ) {
  myObject = i.next();
}

See this Java tutorial about Collections for more info.

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