visualize_code.txt

$ ruby /tmp/viz.rb 
def on_test(ast_node, context)                                | ast_node = "(test nil \"foo\")"
  nodes       = XML::NodeSet.new                              | context = "(something ...)"
  predicate   = ast_node.children[2]                          |
  xpath_index = 1                                             |
                                                              |
  context.each do |xml_node|                                  |
    next unless node_matches?(xml_node, ast_node)             |
                                                              |
    if predicate                                              |
      retval = with_node_set(context) do                      |
        process(predicate, XML::NodeSet.new([xml_node]))      |
      end                                                     |
                                                              |
      # Numeric values are used as node set indexes.          |
      if retval.is_a?(Numeric)                                |
        nodes << xml_node if retval.to_i == xpath_index       |
                                                              |
      # Node sets, strings, booleans, etc                     |
      elsif retval                                            |
        if retval.respond_to?(:empty?) and retval.empty?      |
          next                                                |
        end                                                   |
                                                              |
        nodes << xml_node                                     |
      end                                                     |
    else                                                      |
      nodes << xml_node                                       |
    end                                                       |
                                                              |
    xpath_index += 1                                          |
  end                                                         |
                                                              |
  return nodes                                                |
end                                                           |