Adding two number variables produces NaN?

programming
1

Hi,

In my application I’m calculating the time between each frame with the following:

private function onGameTick(e:Event):void
{
timePrevious = timeCurrent;
timeCurrent = getTimer();
delta = (timeCurrent - timePrevious) * 0.001;
}

I’m then just trying to add that to another number variable like so:

…

private var timePrevious:Number = 0;
private var timeCurrent:Number = 0;
private var delta:Number;
private var testNumber:Number = 0;

…

private function onGameTick(e:Event):void
{
timePrevious = timeCurrent;
timeCurrent = getTimer();
delta = (timeCurrent - timePrevious) * 0.001;

testNumber += delta;
trace(testNumber);

}

I’ve tried casting delta as a Number just to make sure but that doesn’t work… what’s interesting is that I can run:

trace(testNumber+delta);

and that will return the correct result, I just can’t store the result in a variable if any math has been done with the delta variable. I’ve only just gotten back into AS3 so I might be missing some completely fundamental here but I’m clueless at this point so any help is greatly appreciated.

Kind Regards,
Kaine

2

Anything that is defined as Number starts out as Nan. With any number, i always start out defining it as zero.

private var delta:Number=0;

3

Thanks for the response tbo.

Yeah, I’ve tried having it defined as well, no difference. Either way it gets assigned a value before it’s used. Like I was saying the interesting thing is that I can trace something that uses it like:

trace(3+delta);

and that works fine, however if I try to use it with the += operator it just goes to NaN.

4

getTimer returns an int (according to documentation). Maybe that messes things up?

5

That’s why I tried casting it as a number, i.e Number(delta) but that didn’t work. The delta value that is stored is always a decimal anyway… =\

6

You’re telling me that this trace works?

private function onGameTick(e:Event):void {
    timePrevious = timeCurrent;
    timeCurrent = getTimer();
    delta = (timeCurrent - timePrevious) * 0.001;
    trace(testNumber+delta);
}
7

I believe testNumber is Nan, rather than delta. check to see that you defined testNumber before the enterframe is called. I did test and this does work properly in frame 1 on a flash movie

var timePrevious:Number = 0;
var timeCurrent:Number = 0;
var delta:Number=0;
var testNumber:Number = 0;

this.addEventListener(Event.ENTER_FRAME, onGameTick);

function onGameTick(e:Event):void
{
	timePrevious = timeCurrent;
	timeCurrent = getTimer();
	delta = (timeCurrent - timePrevious) * 0.001;

	testNumber += delta;
	trace(testNumber);
}

however if I start with var testNumber:Number; then I get Nan, as Nan+=delta= Nan.
you are correct that delta doesnt matter because its set in that function

edit: does anyone know why my line break spacing is not kept in the post?

8

Yes TheCanadian, that trace works, however if I do:

testNumber+=delta;
trace(testNumber);

I get NaN.

tbo, I’m defining testNumber as 0 so it’s definitely not NaN.

I tried what you said in a flash movie and it works for me too, but when I put the code in my class it doesn’t work -___-… What’s interesting is that if I do this in my function:

var timePrevious:Number = 0;
private var timeCurrent:Number = 0;
private var delta:Number=0;

…

function onGameTick(e:Event):void
{
var testNumber:Number = 0;
timePrevious = timeCurrent;
timeCurrent = getTimer();
delta = (timeCurrent - timePrevious) * 0.001;
testNumber += delta;
trace(testNumber);
}

it works fine, however if I declare the variable in the class rather than the function I get NaN.

EDIT:
I created a new project with the code in the main class and it works, so it’s something about my current class in my current project, even though the classes are basically identical.

9

Perhaps if you post the whole class.

At the point where you have the += problem. What if you just trace testNumber by itself? Or delta, surely one of them must be nan at that time

10

So I found that timeCurrent was NaN, I just rewrote the class, making sure I did everything correctly and it’s working.

Still find it bizarre that I could do arithmetic in a trace statement and it would produce the correct results however if trying to assign that to a variable it didn’t like it. Oh well, it’s fixed now!

Thanks for all your help!

11

Well, the good thing with Flash and actionscript - it fosters generalist rather than specialist.

-“Did you find the error?”
-“Yes, I rewrote the code”

12

I find that bizarre, too.

13

I think the [ code][ /code] tags don’t work properly. It seems to work if you use three grave accents (`) before and after your code (if that makes any sense).

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