private void loadSourceLines(String baseFileName) throws IOException {
        sourceLines = new ArrayList<SourceLine>();
        sourceLines.add(new SourceLine(""));
        BufferedReader reader = new BufferedReader(new FileReader(baseFileName
                                                                  + ".x"));
        String line;
        for (int i = 1; (line = reader.readLine()) != null; i++) {
            sourceLines.add(new SourceLine(line));
        }
    }