Queue's

Box

Hi

Im unsure of how to do this. Spent most of yesterday trying various things but just ran into error after error and am now lost.

Basically I have a timer than runs every 10ms. It works out a value each time and I want to know the value it worked out 2.5 seconds ago.

My thoughts on doing this would be to have the value added to a queue once it is up to 250 I can start reading back. The logic seems easy enough to me. I just dont know how to put it into practice.

How can I 'globalise' the queue so that it isnt destroyed each time in the timer.

People suggested using a static class along the lines of

static class globalSpeed
{
private static Queue gSpeed = new Queue();
public static string Speed
{
get { return gSpeed; }
set { gSpeed = value; }
}
}

but this gave all kinds of errors. static errors, conversion errors.

Can someone please point me in the right direction to go about this.

thanks

8 Replies

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Vulpes14y ago
Accepted answer
Well, I'd have thought that all you needed to do was to declare the Queue as a field of whatever form or class the timer's Tick event is declared in.

Something like this assuming the value to be worked out is a double:

private Queue speed = new Queue(250);

private void timer1_Tick(object sender, EventArgs e)
{
double d = WorkoutValue();
speed.Enqueue(d);

if (speed.Count > 250)
{
double e = speed.Dequeue();
// do something with e
}
}
0
Box14y ago
ahhh thatll be it then. were on 2002

in that case i'll cast the obkects to doubles

q.Enqueue(d);
if (q.Count > 50)
{
s = (double)q.Dequeue();
}
else
{
s = (double)q.Peek();
}

s = d - s;
s *= 3600;

Well cheers for the help. its been very useful :)
0
Vulpes14y ago
It sounds like you may be using an older version of Visual Studio - 2002 or 2003 - which doesn't support generics. These were introduced in VS 2005.

If that's the case, you'll have to use the non-generic Queue class - there's no other (easy) alternative.
0
Box14y ago
C:\Documents and Settings\m194012\My Documents\Visual Studio Projects\InTheDistance\Form1.cs(329): Invalid token '<' in class, struct, or interface member declaration
C:\Documents and Settings\m194012\My Documents\Visual Studio Projects\InTheDistance\Form1.cs(329): Invalid token '>' in class, struct, or interface member declaration
C:\Documents and Settings\m194012\My Documents\Visual Studio Projects\InTheDistance\Form1.cs(329): Invalid token '=' in class, struct, or interface member declaration
C:\Documents and Settings\m194012\My Documents\Visual Studio Projects\InTheDistance\Form1.cs(329): Invalid token '<' in class, struct, or interface member declaration
C:\Documents and Settings\m194012\My Documents\Visual Studio Projects\InTheDistance\Form1.cs(329): Invalid token '>' in class, struct, or interface member declaration

I just get 5 errors on that line now.

is this perhaps a version thing? im at work and they dont really like to have the latest versions of software (we still using windows xp, office 2002 and IE6!)
0
Vulpes14y ago
Just noticed in your previous post that you had the <> and the () the wrong way around, viz:

private Queue q = new Queue();

should be:

private Queue q = new Queue();

Notice also that if you specify the capacity - 250 or perhaps 251 here - in the constructor, then this prevents the Queue's internal array from having to be resized a number of times before 250 is reached:

private Queue q = new Queue(251);
0
Box14y ago
well i would only be storing numebrs and I dont want to be running inefficient code intentionally. I just get errors when i use the triandle brackets saying invalid token :| i'll try the object one for now but ideall want to know why It wont be declared as a double
0
Vulpes14y ago
I'm using the generic Queue in the above code where the values all have to be of the same type - 'double' in my example but they could be anything else you like. For example a Queue can only contain strings.

There's also a non-generic Queue which can take any type of value - internally it converts them all to Object which is slow if you want to store simple value types such as double, int etc.

However, if you'd prefer to use that instead, the code would become:

private Queue speed = new Queue(250);

private void timer1_Tick(object sender, EventArgs e)
{
object o = WorkoutValue();
speed.Enqueue(o);

if (speed.Count > 250)
{
object p = speed.Dequeue();
// do something with p
}
}
0
Box14y ago
Thanks for this. Its a great help! Getting much closer to having it working. I've got all the code in to do what I need to do with the queue. im just struggling to have it as a double :|

private Queue q = new Queue();

causes errors:
queue invalid token '<' in class struct or interface member declaration c#

and when taking the out it gives an error saying:

Cannot implicitly convert type 'object' to 'double'

:|
0