function name ( [type1 param1, type2 param2, ... ] )

Declares a custom function in your script. A function is a way in which you can separate out commonly used code into its own place, and thus avoid duplicating code.

For example, suppose that you quite often want to play a sound and add an inventory item at the same time. You could write both commands each time, or you could define a custom function:

function AddInvAndPlaySound(int inventoryItem) {
  player.AddInventory(inventory[inventoryItem]);
  PlaySound(5);
}

then, elsewhere in your code you can simply call:

AddInvAndPlaySound(8);

Generally, you place your functions in your global script. You then need to add an import line to your script header to allow the function to be called from room scripts.

Optional parameters

You can make int parameters optional if there is a default value that the user doesn't need to supply. To do this, change the script header import declaration like this:

import function TestFunction(int stuff, int things = 5);

NOTE: To use optional parameters, you need to have an "import" declaration for the function in the script header. The default values cannot be specified in the actual function declaration itself.