How to do this

Hi, I'm new to scripting and I have a question... Is there any way to change a variable? Say I have a value that will, over time increase. How can I do this? Say I want a number to go up when the object recieves a command, what should I do?

Declare the variable, maybe as a global (above the default state)

e.g.

integer counter;

then either counter++ or ++counter will do it.

Receives a command? Well it needs to go in an event, you just put it in there. Say you want it to receive a command by touch it would go

touch_start(integer number)
{
    counter++;
    // do anything else
}

From the Wiki "Note: a default value is specified, and it should be expected by the programmer that this value will not change at runtime. " (In reference to variables).

Is there any way for it to change at runtime, and store it? By perhaps writing to a notecard? The value I need to change in runtime, and still be different upon the next rez. How is this possible?

Test it to be sure, but I'm pretty sure that as long as you don't set a default value it won't change on rez. Something like this should do:

integer counter;
default
{
    on_rez(integer times)
    {
        llSay(0, (string)counter);
        counter++;
    }
}

If it does clear the counter each time the best bet, for something like that, is to store it in the item description. There is no sure way to store large amounts of data in SL yet, but a number you can hide here or in other ways if you need people not to be able to see the number with a mouseover - llSetAlpha() or llSetScale() or similar, then use the corresponding llGet () functions to read it back.

Probably simplest and most reliable would be...

llSetObjectDesc((string)my_counter);

...you could hide it on a linked child prim if you were feeling fancy.
/esc

Could I do counter-- to subtract from it?

yup

Hmm... And what if I wanted to subtract an amount higher than 1, and wanted a starting number other than 0?

lol.

Try http://secondlife.com/badgeo/wakka.php?wakka=operators

but you assign using =, e.g.

integer counter = 66;

counter +=5 or counter = counter + 5 will both do.
counter -=23 or counter = counter - 23 similarly.

float counter = 2.1728

counter = counter * PI will work too...

I want to be able to do counter-- when the if llListen(50, "", "","bang"; . How would I do this? I can't seem to do it with if.

listen(integer channel, string name, key id, string message)
{
    if(channel == 50 && message == "bang")
    {
        counter++;
    }
}

Can I suggest the scripting library and Crash Course might be good places to start you off, see how others have done these things...

I'm glad Eloise finally gave the big picture there. I was worried that Leb would start using counter--; counter--; counter--; counter--; to subtract 4. And that would be uncool. C'mon people, no half-assed explanations. To add a bit,

counter += 5 is the same as saying counter = counter + 5

That's good for incrementing or decrementing by more than 1.