class REXML::Parsers::XPathParser

def AdditiveExpr path, parsed
  n = []
  rest = MultiplicativeExpr( path, n )
  if rest != path
    while rest =~ /^\s*(\+|-)\s*/
      if $1[0] == ?+
        n = [ :plus, n, [] ]
      else
        n = [ :minus, n, [] ]
      end
      rest = MultiplicativeExpr( $', n[-1] )
    end
  end
  if parsed.size == 0 and n.size != 0
    parsed.replace(n)
  elsif n.size > 0
    parsed << n
  end
  rest
end