Readable Conditionals

By Zevan | March 4, 2009
CLICK HERE TO COPY
Actionscript:
  1. // NOTE: this code won't do anything in you're timline....
  2.  
  3. // do you do this?
  4.  
  5. if (ball.x <0 || ball.y <0 || ball.x> stage.stageWidth || ball.y> stage.stageHeight){
  6.        // cause ball to explode
  7. }
  8.  
  9. // or this?
  10.  
  11. if (isAtStageEdge(ball)){
  12.        // cause ball to explode
  13. }
  14.  
  15. function isAtStageEdge(mc:MovieClip):Boolean{
  16.    return (mc.x <0 || mc.y <0 || mc.x> stage.stageWidth || mc.y> stage.stageHeight);
  17. }

This is pretty standard stuff, but it can increase code readability especially for complex conditionals.

I also do this if I find myself repeating an a semi-complex if statement in two or more places.

If I'm just brainstorming I probably won't bother, but on real projects it helps keep code readable.

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String.fromCharCode()

By Zevan | March 3, 2009
CLICK HERE TO COPY
Actionscript:
  1. [SWF(height = 950, width=1000)]
  2. var txt:TextField;
  3. var num:int = 0;
  4. for (var i:int = 0; i<761; i++){
  5.     if (i % 76 == 0){
  6.          makeTxt(num);
  7.          num++;
  8.     }
  9.     if (i <0x21){
  10.         txt.appendText("-\n");
  11.     }else{
  12.         txt.appendText(String.fromCharCode(i) + " = " +  i + "\n");
  13.     }
  14. }
  15. function makeTxt(num:Number):void{
  16.      txt= TextField(addChild(new TextField()));
  17.      txt.x = 10 + num * 100;
  18.      txt.y = 10;
  19.      txt.height = 930;
  20.      txt.text = "";
  21. }

This will draw a few columns of char codes.

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String.localeCompare()

By Zevan | February 28, 2009
CLICK HERE TO COPY
Actionscript:
  1. var letterA:String = "a";
  2. var letterZ:String = "z";
  3.  
  4. trace(letterA.localeCompare(letterZ));
  5. trace(letterZ.localeCompare(letterA));
  6. /*
  7. outputs
  8. -25
  9. 25
  10. */

String.localeCompare() calculates the sorting order between two Strings....

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Random Sort

By Zevan | February 27, 2009
CLICK HERE TO COPY
Actionscript:
  1. function randomize(a:*, b:*):int{
  2.        return Math.round(Math.random()*8) - 4;
  3. }
  4.  
  5. var i:int;
  6. var fruits:Array;
  7.  
  8. trace("Math.random()");
  9. for (i = 0; i<4; i++){
  10.   // reset fruits array:
  11.   fruits = ["apple", "grape","pear","cherry"];
  12.   fruits.sort(randomize);
  13.   trace(fruits);
  14. }
  15.  
  16.  
  17. // seeds
  18. var s1:Number= 0xFF00FF;
  19. var s2:Number = 0xCCCCCC;
  20. var s3:Number= 0xFF00F0;
  21.  
  22. function tRandomize(a:*, b:*):int{
  23.        return Math.round(rand()*8) - 4;
  24. }
  25.  
  26. trace("\nTausworthe rand()");
  27. for (i= 0; i<4; i++){
  28.   fruits = ["apple", "grape","pear","cherry"];
  29.   fruits.sort(tRandomize);
  30.   trace(fruits);
  31. }
  32. // from www.ams.org/mcom/1996-65-213/S0025-5718-96-00696-5/S0025-5718-96-00696-5.pdf
  33. function rand():Number {
  34.     s1=((s1&4294967294)<<12)^(((s1<<13)^s1)>>19);
  35.     s2=((s2&4294967288)<<4)^(((s2<<2)^s2)>>25);
  36.     s3=((s3&4294967280)<<17)^(((s3<<3)^s3)>>11);
  37.     var r:Number = (s1^s2^s3) * 2.3283064365e-10;
  38.     r = (r<0) ? r+=1 : r;
  39.     return r;
  40. }
  41.  
  42. /*
  43. outputs:
  44. Math.random()
  45. grape,apple,pear,cherry
  46. pear,cherry,apple,grape
  47. grape,apple,pear,cherry
  48. grape,apple,cherry,pear
  49.  
  50. Tausworthe rand()
  51. apple,grape,pear,cherry
  52. cherry,grape,pear,apple
  53. grape,apple,cherry,pear
  54. grape,pear,apple,cherry
  55. */

The above shows how to randomly sort or shuffle an array. This is useful in games. To achieve this I made use of the compareFunction argument of Array.sort(). Most sorting algorithms go through the array and compare values until the desired sort order is achieved. The compareFunction argument is a function that takes two values a and b and returns an integer that is negative positive or zero... see this info from the docs:
* A negative return value specifies that A appears before B in the sorted sequence.
* A return value of 0 specifies that A and B have the same sort order.
* A positive return value specifies that A appears after B in the sorted sequence.

So in the case of a randomizing an array you simply need to return a random int -1, 0 or 1. This is what I've done in the past (Math.round()*2) -1) ... but when I was writing this snippet it seemed like 0 caused less variation in the output of the array so I made the range from -4 to 4 instead. This could have just been my imagination, but it seems like having less chance of a zero caused the arrays to be a bit more shuffled.

The reason I also included a version that uses Tausworthe is because of the easy seeding. In some cases you may want to use seeded randomness to sort an array.

UPDATE:
Was digging around about this and found a much faster method for randomizing arrays... not a big deal if you have small arrays, but if you need to randomize 1000's of values this method is much faster than using Array.sort()

Posted in arrays, misc | Tagged , | Leave a comment