What is the best way to check if the NPC you're in dialog with is a merchant?

I consider using OBSE's GetServicesMask funtion, and then use the result and make a LogicalAnd with 13727 (all service flags except Spells, Training, Recharge and Repair) - or simply calling all the relevant OffersXXX functions and assuming he is a merchant if at least one returns true.

But is there a simpler way of finding out if he is a merchant?

Too bad nobody answered my previous question, I'll try with something more practical.
I'm trying to make a script that will add crime gold to your character if you try to sell something "illegal", but I don't know how to force an exit of the bartering menu or some way to avoid the sell to take place. Is there some way? Also, what's better or less prone to conflicts, using modcrimegold or setcrimegold?

GetParentCell returns the ObjectID of the cell the reference is in.

Can this be passed to PositionCell in place of the cell name?

GetServices would be best way for Modded Merchants, Since there are some merchants that do not have services until they are activated once again.

I guess you're talking Tamriel Travellers here.

If they're not of one of the normal merchant classes, then I need additional checks (like seeing if the barter button is visible, or whether they offer relevant services), as it is highly important to not miss out on anyone that can be traded with.

How do you make an NPC perform a specific animation? Not sure if that's a simple question.

Is an actor just NPCs or is it NPCs and creatures?

What's the maximum number of items you can have in one container? I know the more items, the more lag you will get opening the inventory, but I was wondering if there's a fixed limit.

. . . Am I missing something obvious about PositionCell?

Yup! 57.3 is the number! Any number you use for zRot gets multiplied by 57.3 by positionCell. A bug, of course, although I can't imagine why 57.3.

An array is a series of variables that are stored together. So, for example, in a baseball game you could have an array of scores for each team in each inning - say, two arrays of nine integers. So you'd have Team1Score, which is an array, and Team1Score[0] is their score in the 1st inning, Team1Score[1] is their score in the 2nd inning, etc etc. Team2Score[0] would be the other team's score in the 1st, etc.

You could just have 18 variables - Team1Score1st, Team1Score2nd, etc. But what happens if the game goes to extra innings? You could have more variables defined, but you have a limit - however many you need. You could have 60 variables, 30 innings each; that will probably be enough (record for an MLB game is 26 innings), but now you have 42 variables more than you'll usually need. But when you have an array, you can just refer to Team1Score[9] for the 10th inning, and the code will create a slot for Team1Score[9] the first time you assign something to it (in Oblivion script; some programming languages require preparation of the slot first).

Further, you can refer to an inning with a variable. So instead of something like this to add a run to Team 1:

if ( inning == 1 )	set Team1Score1st to Team1Score1st + 1elseif ( inning == 2 )	set Team1Score2nd to Team1Score2nd + 1etc

You can just do this:

Team1Score[inning] = Team1Score[inning] + 1

This kind of just touching the tip of the iceberg; there's a lot more you can do with arrays. For example, you can have multidimensional arrays - like a table, perhaps. So you could actually just do Score[0][2] for Team 1's score in the 3rd.

The big thing to remember is that arrays start at 0. It can be easy to forget that.

OBSE arrays can also have things other than numbers as the "key", so you can do something like have an array called NPC, which stores a variety of information about an NPC, and then use NPC[name] to get its name, or NPC[lastSpokeTo] to get the time when you last spoke to them. Or whatever, it's up to you to define how they're used.

What you said about the array[0][1]: Des that mean I can have array[0] be a weapon reference and array[0][1] be the weapon reference's reach?

And how many variables are allowed per array?

That shows how a[0] is an array of three values, a[0][0], a[0][1], and a[0][2]. This is a 3x3 array because a is an array of 3 arrays of three elements. You can have non-square arrays (e.g. 100x5), you can have arrays of more dimensions (e.g. 3x4x5), and in OBSE you can even have arrays of differing lengths (though this is not recommended because it can be very difficult to keep track of).