Question

How can i generate dynamically this array.

var posX:Array = [0,-20,20,-40,0,40,-60,-20,20,60,-80,-40,0,40,80,-100,-60,-20,20,60,100]

The numbers in the array refer to the x position of the object. I use it to place objects in triangular formation.

     0
   -20 20
  -40 0 40
-60 -20 20 60 etc

Thank you in advance

Answer 1

var d:Number = 20;
var a:Array = [];
for(var i:Number = 0; i < 6; i++)
{
    for(var j:Number = 0; j <= i; j++)
    {
        a.push(d * (2 * j - i));
    }
}
trace(a.join());    

The first number of each row is the negative of the zero-based-row-index times d : which is - i * d
Each subsequent number in a row exceeds the previous one by 2*d. Hence subsequent numbers = first-element + 2 * d * zero-based-index-within-the-row

Which is = - i * d + 2 * d * j = d * (2 * j - i)