By Zevan | April 11, 2009
Actionscript:
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var a:Vector.<Sprite> = new Vector.<Sprite>();
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trace("unsorted");
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for (var i:int = 0; i<10; i++){
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var s:Sprite = new Sprite();
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s.x = int(Math.random()*100);
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a.push(s);
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trace(s.x);
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}
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quickSortOn(a, "x", 0, a.length-1);
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trace("sorted");
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for (i= 0; i<10; i++){
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trace(a[i].x);
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}
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// modified code from kirupa.com
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// http://www.kirupa.com/developer/actionscript/quickSort.htm
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function quickSortOn(a:Vector.<Sprite>, prop:String, left:int, right:int):void {
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var i:int = 0, j:int = 0, pivot:Sprite, tmp:Sprite;
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i=left;
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j=right;
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pivot = a[Math.round((left+right)*.5)];
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while (i<=j) {
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while (a[i][prop]<pivot[prop]) i++;
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while (a[j][prop]>pivot[prop]) j--;
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if (i<=j) {
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tmp=a[i];
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a[i]=a[j];
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i++;
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a[j]=tmp;
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j--;
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}
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}
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if (left<j) quickSortOn(a, prop, left, j);
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if (i<right) quickSortOn(a, prop, i, right);
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}
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/* outputs something like:
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unsorted
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26
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33
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20
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63
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7
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68
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75
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39
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67
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53
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sorted
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7
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20
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26
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33
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39
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53
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63
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67
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68
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75
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*/
This demo is my first quick stab at using at a sortOn() function for the Vector class. It sorts a Vector of Sprites by their x property.
Recently there were a few times when I was prototyping ideas and suddenly realized that I needed to change my Vector to an Array because I needed to use sortOn().(If you don't already know, there is no built in sortOn() method for the Vector class). In the past I spent some time with sorting algorithms, bubble, insertion etc... so I knew I could pretty easily write my own sortOn(), but I also realized that a generic implementation wouldn't be easy/possible without loosing the type of the Vector. What I mean is, if you have a Vector of Sprites, you need a sorting method that takes a Vector.< Sprite > type as an argument (as seen above), if you have a Vector of TextFields you need a Vector.< TextField > type as an argument. You could of course use a generic type, but this kind of defeats the purpose of using a vector in the first place...
I will likely post a revised version of this in the near future with a slightly improved implementation of QuickSort. I haven't spent that much time with this, but If I recall correctly this is not the ideal implementation. I ported this code from a nice Kirupa tutorial and modified it to sort based on a property...
By Zevan | April 10, 2009
Actionscript:
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var xn:Number = 1;
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var xn1:Number = 0
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var square:Number =39;
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trace("find the sqrt of ", square);
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trace("Math.sqrt: ", Math.sqrt(square))
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// no starting approximation, just try up to 35 iterations
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for(var i:int = 0; i<35; i++){
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xn1 = .5 * (xn + square / xn);
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if (xn1== xn){
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trace("other sqrt: ", xn1);
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break;
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}
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xn = xn1;
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}
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/*outputs
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find the sqrt of 39
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Math.sqrt: 6.244997998398398
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other sqrt: 6.244997998398398
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*/
I was reading about calculating square roots - not for speed optimization purposes, just to see some of the different ways to go about it. The above snippet uses the Babylonian method to find the square root of a number. I left out the first step of guessing at the square root... so this snippet is by no means efficient...
Posted in Math | Tagged actionscript, flash |
Actionscript:
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// Superformula (equations from):
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// http://www.geniaal.be/downloads/AMJBOT.pdf
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// http://en.wikipedia.org/wiki/Superformula
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const TWO_PI:Number = Math.PI * 2;
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function superShape(a:Number, b:Number, m:Number, n1:Number, n2:Number, n3:Number, pnt:Point, scale:Number):void{
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var r:Number = 0
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var p:Number = 0;
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var xp:Number = 0, yp:Number = 0;
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while(p <= TWO_PI){
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var ang:Number = m * p / 4;
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with(Math){
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r = pow(pow(abs(cos(ang) / a), n2) + pow(abs(sin(ang) / b), n3),-1/n1);
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xp = r * cos(p);
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yp = r * sin(p);
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}
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p += .01;
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canvas.setPixel(pnt.x + xp *scale, pnt.y + yp * scale, 0xFFFFFF);
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}
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}
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// test it out:
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var canvas:BitmapData = new BitmapData(700,600,false, 0x000000);
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addChild(new Bitmap(canvas, "auto", true));
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superShape(1, 1, 5, 23, 23, 23, new Point(100,80), 30);
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superShape(1, 1, 5, 13, 13, 3, new Point(200,80), 30);
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superShape(1, 1, 8, 3, 13, 3, new Point(300,80), 30);
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superShape(10,8, 16, 30, 13, 3, new Point(450,80), 30);
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superShape(1,1, 1, .5, .5, .5, new Point(100,190), 100);
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for (var i:int = 0; i <150; i++){
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superShape(1,1, 2, 1+i/800, 4, 8-i * .1, new Point(550,350), 50);
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}
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for (i = 0; i <20; i++){
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superShape(1.1,1.2, 6, 2 + i , 4, 9 - i, new Point(200,350), 50);
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}
The above snippet demos a function that will draw Supershapes using the Superformula...
From wikipedia:
The Superformula appeared in a work by Johan Gielis. It was obtained by generalizing the superellipse, named and popularized by Piet Hein...
Here is the result of the above code:
You can read more about the Superformula here in the original paper by Gielis.
wikipedia entry...
3d Supershapes by Paul Bourke
Actionscript:
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var target:Number = 1024;
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var slices:Array = [target];
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var leng:int = 11;
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for (var i:int = 0; i<leng-1; i++){
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var index:int = int(Math.random()*slices.length);
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var val:Number = slices[index];
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var rand:Number = Math.random() * val/2;
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slices[index] = val - rand;
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slices.push(rand);
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}
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trace(slices);
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// test that they all add up
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var sum:Number = 0;
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for (i = 0; i<slices.length; i++){
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sum += slices[i];
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}
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trace("test that they all add up: ", sum);
The above snippet creates an array of a specified length whose elements all add up to the variable target. Here is some example output:
165.31133050055192,322.23456030456015,
257.47582363389245,26.9984893942173,1.96283924962002,
5.466277873168191,21.362282634705164,62.68168197512457,
76.63028224500404,36.27274381401516,12.558309228795265,35.04537914634583
test that they all add up: 1024