clock.Reset() setting clock to weird time

[nano511]

Im trying to make a target launcer fire a target every 5 seconds. The problem is that the clock starts acting funny after the first target is launched. Here is the log from the console:

1	clock:4.61451 amountofT: 0
2	clock:4.8168 amountofT: 0
3	degree: 14   force: 14
4	clock:2.54222e-005 amountofT: 1
5	clock:0.191573 amountofT: 1
6	clock:0.394454 amountofT: 1

amountofT is the amount of targets that are currently in the game. degree and force are cout'ed right before the target is fired. My question is why do i get that "clock:2.54222e-005"? This problem is also causing targets to be fired prematurely and then i get some kind "list iterator not incrementable" Debug Assertion Failed message.

Here is the code:

01	//Launch A Target Every 10 Seconds
02	if(clock.GetElapsedTime() >= 5){
03	    //Launch target
04	    srand(time(NULL));
05	    int degree = rand() % 15;
06	    int force = rand() % 20+5;
07	    Target *target = new Target(xPos, yPos, degree, force);
08	    targets.push_back(target);
09	 
10	    std::cout<<"degree: "<<degree<<"   force: "<<force<<std::endl;
11	 
12	    //Reset clock
13	    clock.Reset();
14	    }
15	 
16	         std::cout<<"clock:"<<clock.GetElapsedTime()<<" amountofT: "<<         targets.size()<< std::endl;

[Moschops]

"clock:2.54222e-005"

Seems pretty reasonable to me. You reset the clock, and then you ask it how much time has elapsed since it was reset, and it says 25 micro-seconds.

[nano511]

Ahh okay the problem seems to be with removing the target once it has crashed. When the target collides i want it to be removed, but instead i get a "list iterator not incrementable" Debug Assertion Failed message. Here is the relevant code:

//In TargetLauncher::Update()
	//Launch A Target Every 10 Seconds
	if(clock.GetElapsedTime() >= 5){
		//Launch target
		srand(time(NULL));
		int degree = rand() % 15;
		int force = rand() % 20+5;
		Target *target = new Target(xPos, yPos, degree, force);
		targets.push_back(target);

		std::cout<<"degree: "<<degree<<"   force: "<<force<<std::endl;

		//Reset clock
		clock.Reset();
	}

	//Update each target
	if(targets.size() > 0)
		for( std::list<Target*>::iterator i = targets.begin(); i != targets.end(); ++i)
		{
			if( (*i)->Update(window) == REMOVE )
				targets.erase(i);
		}

	std::cout<<"clock:"<<clock.GetElapsedTime()<<" amountofT: "<< targets.size() << std::endl;

	return KEEP;

//In Target::Update()
Target::State Target::Update(sf::RenderWindow& window)
{
	//Move the target
	CollideWithMap(window);
	xPos += xVel;
	yPos += yVel;

	yVel += GRAVITATION;

	sprite.SetPosition(xPos - scroll_X, yPos - scroll_Y);

	//If the target collides with something, return REMOVE
	if(broken) return REMOVE;

	return KEEP;
}

CollideWithMap sets 'broken' to true if it collides with the map. Remove is returned. Then i get "Debug Assertion Failed!...list iterator not incrementable" because the for loop continues for some reason.

[Moschops]

Let's say there are 5 elements in the list, and they contain letters a to e, like this: a,b,c,d,e.

You're at the 4th element; that is, list[i] where i=3. You decide to delete it. Now, the list looks like this:

a,b,c,e

You're still at list[3], which is now the element with the e in it.

Now you increment the iterator. Oh no! You've just incremented the iterator to position 4 in the list, but that doesn't exist! You've incremented an iterator when you shouldn't, because you're not allowed to increment an iterator beyond the end of the list, and it crashes.

[nano511]

Shouldn't it stop looping since i now equals list.end()?

	for( std::list<Target*>::iterator i = targets.begin(); i != targets.end();++i;)
	{
		if( (*i)->Update(window) == REMOVE )
				targets.erase(i);
	}

How do i fix this?

[Moschops]

Shouldn't it stop looping since i now equals list.end()?

When is that checked? Before starting each new loop. What happens at the end of the current loop, even though we're now at list.end()? i++.

Just don't increment in a loop where you erase.

[nano511]

Okay i changed it to

for( std::list<Target*>::iterator i = targets.begin(); i != targets.end();)
	{
		if( (*i)->Update(window) == REMOVE )
				targets.erase(i);
		else
			i++;
	}

And now i get "Debug Assertion Failed!...list iterators incompatible" upon removal.

[nano511]

Aha i found the answer. I needed to do i= targets.erase(i) instead of just targets.erase(i)