Provide a common base for different types for Prolog atoms.
Inheritance: PrologCodeTerm
        public PrologCodeTerm ConvertBinaryTreeToCodeDOM(BinaryTree tree)
        {
            // Clause
            if (tree.Name == ":-")
            {
                PrologCodeClause term = new PrologCodeClause();
                if (tree.Left != null)
                {
                    ArrayList goals = new ArrayList();
                    tree.Flatten(tree.Right, ref goals);
                    foreach (BinaryTree goal in goals)
                    {
                        term.Goals.Add(ConvertGoalBinaryTreeToCodeDOM(goal));
                    }
                    term.Head = (PrologCodePredicate)ConvertBinaryTreeToCodeDOM(tree.Left);
                    return term;
                }
                // Headless clause
                else
                {
                    // process headless clause here
                    PrologCodeHeadlessClause hClause = new PrologCodeHeadlessClause();
                    ArrayList goals = new ArrayList();
                    tree.Flatten(tree.Right, ref goals);
                    foreach (BinaryTree goal in goals)
                    {
                        hClause.Goals.Add(ConvertGoalBinaryTreeToCodeDOM(goal));
                    }
                    return hClause;
                }
            }
            else if (tree.Name == ".")
            {
                return ConvertBinaryListToCodeDOM(tree);

            }
            // Variable
            else if (Char.IsUpper(tree.Name[0]))
            {
                if (tree.Left != null || tree.Right != null)
                {
                    ParserError("Something was not parsed right. Variable has arity > 0", 0, 0);
                }
                PrologCodeVariable var = new PrologCodeVariable(tree.Name);
                return var;
            }
            else
            {
                return ConvertGoalBinaryTreeToCodeDOM(tree);
            }
            //return null;
        }