// COMP1405/1005 - Day 10
// Array example

// variables
int x[];   // variable x is an array of integers
int y[];   // variable y is an array of integers
int diam;  // diamater of balls drawn
int num;     // number of balls to draw at one time


// initialization
void setup() {
  size(800, 600);

  // number of balls to draw on the screen
  num = 1000;

  // Ask Processing/Java for memory for the arrays
  // Unitl we use the "new" command the variables x and y
  // are just names that can/will point to an array
  // (but don't yet)
  x = new int[num];
  y = new int[num];

  // After calling "new" we have memory for the arrays
  // but nothing is "in" the arrays yet.
  // Let's populate the arrays with data
  for ( int i = 0; i < num; i+=1) {
    x[i] = (int) random(25, width-25);
    y[i] = (int) random(25, height-25);
  }

  diam = 25;
}


// main program
void draw() {
  // draw "num" balls using the (x,y) coordinates
  // given by the arrays x and y 
  int i = 0;
  while (i < num) {   
    ellipse(x[i], y[i], diam, diam);
    i+=1;
  } 

  // update the position of all "num" balls
  // (notice that for loop is probably easier to use
  //  than while loop for this purpose.  We know
  //  exactly how many times to iterate, so use a for loop)
  for (int j=0; j < num; j+=1) {
    x[j] += (int) random(-2, 2);
    y[j] += (int) random(-2, 2);
  }
}