Problem with Array

[Cortana]

Im making a game which relies on multidimensional arrays. But Im getting a serious problem which can be reproduced with this code (in the Flash 9 preview)

var test:Array = new Array()
test.push(["a", "b"])
test.push(["c", "d"])
trace(test[0][0])	//	a
trace(test[1][0])	//	c
trace(test[0][-1])	//	undefined (perfectly acceptable)
trace(test[-1][0])	//	throws error : "TypeError: Error #1010: A term is undefined and has no properties."

How can i get around this error? It's annoying because I actually want it to return undefined!

[senocular]

check for valid objects before referencing their properties or use try-catch

http://www.kirupa.com/forum/showthre...71#post2098271

[ghfhg]

test[0][-1] is ok because test[0] exists, though test[0][-1] is undefined.

test[-1][0] is an error because test[-1] is undefined and you're in effect trying to access a property([0]) of an object that does'n exist. In AS3 you have to do bounds checking to avoid these errors.

[Cortana]

Damn Adobe! I understand now I'll need to change my code a bit to avoid the error which will probably add a few milliseconds to each frame. Grumble!

[senocular]

an if clause takes far less to complete than even a single millisecond. In fact, lets see if it can be timed. Working off of the following code:

var notDefined:Object;
var timer:Number = getTimer();
var count:Number = 0;
while(true){
	if (notDefined){}
	count++;
	if (getTimer() - timer >= 1000) break;
}
trace(count);

ran 10 times, throwing out the highest and lowest, I get an average of 5719602 iterations for a second. Now, thats not considering the time taken for the count++ and timer code. Running that on its own (the above code without the if statement) got me an average of 6273903 iterations. That equates to ... after carrying the 1... and a 4, 3 - niner ... about, well we'll round it to roughly 75000000 - that's 75 million if conditions that can be evaluated every second, or 75 thousand every millisecond.

I don't think you have anything to worry about.

[Cortana]

Indeed right you are! I tested your code in Flash 8 and 9 and executing that code showed me that it could execute almost 10 times the amount of 'if' statements in Flash 9 compared to 8. Im quite impressed.

Thanks for your time