Building A Second Life Checkers Game #2

I'm making progress on the checkers game and thought I would talk about some of the data structures.

The available LSL data structures are quite limited, but enough to make scripts that do anything.

The biggest thing you learn early on is that there are no arrays. At least not like in other languages. What they do have are lists which are basically arrays, but you have to use special functions to manage the arrays.

As an example, I know my board has 32 spaces so I have a list that contains the piece number at any given space. You first have to allocate space for the 32 spaces.

list board;

InitializeBoard()
{
  integer i=0;
  for(;i<32;i++)
  {
    llListInsertList(board, [-1], 0);  // -1 means no piece is there
  }
}

As I traverse through the linked pieces (see previous entry), I insert them into the board at their location which is defined with a little CSV in their title "r,1,1". The first letter is the color, the second is the piece number and the third is the location which are the same. I may have over designed the piece number and location...

Once you know the piece number you can add it to the data structure (list) holding the locations on the board.

board = llListReplaceList(board,[piece_num],piece_location,piece_location);

One thing to note, ReplaceList creates a whole new list and returns it. You WILL at some point screw this up and not have the board = in there and wonder why your list update didn't occur. It is just part of the learning curve. I'm sure I'll do it again and again and waste more hours. I think the compiler should warn you of this since it seems so necessary and such a common mistake.

When you want to access an element in the list you do so knowing the type that you previously stored in the list. In this case it was an integer and if I want to know what was at location 3, I would do this.

integer pieceAtLocation = llList2Integer(board,3);

For other types stored in lists, there are other functions, llList2String, llList2Vector, llList2Key, etc...