first

# File lib/rexml/xpath_parser.rb, line 92
    def first( path_stack, node )
      return nil if path.size == 0

      case path[0]
      when :document
        # do nothing
        return first( path[1..-1], node )
      when :child
        for c in node.children
          r = first( path[1..-1], c )
          return r if r
        end
      when :qname
        name = path[2]
        if node.name == name
          return node if path.size == 3
          return first( path[3..-1], node )
        else
          return nil
        end
      when :descendant_or_self
        r = first( path[1..-1], node )
        return r if r
        for c in node.children
          r = first( path, c )
          return r if r
        end
      when :node
        return first( path[1..-1], node )
      when :any
        return first( path[1..-1], node )
      end
      return nil
    end