class IsoDoc::Iso::Xref

def sequential_figure_names(clause)
  j = 0
  clause.xpath(ns(FIGURE_NO_CLASS)).noblank
    .each_with_object(IsoDoc::XrefGen::Counter.new) do |t, c|
    j = subfigure_increment(j, c, t)
    sublabel = j.zero? ? nil : "#{(j + 96).chr})"
    figure_anchor(t, sublabel, c.print, "figure")
  end
  sequential_figure_class_names(clause)
end