class IRB::SLex::Node

def match(chrs, op = "")
  D_DETAIL.print "match>: ", chrs, "op:", op, "\n"
  if chrs.empty?
    if @preproc.nil? || @preproc.call(op, chrs)
      DOUT.printf(D_DETAIL, "op1: %s\n", op)
      @postproc.call(op, chrs)
    else
      nil
    end
  else
    ch = chrs.shift
    if node = @Tree[ch]
      if ret = node.match(chrs, op+ch)
        return ret
      else
        chrs.unshift ch
        if @postproc and @preproc.nil? || @preproc.call(op, chrs)
          DOUT.printf(D_DETAIL, "op2: %s\n", op.inspect)
          ret = @postproc.call(op, chrs)
          return ret
        else
          return nil
        end
      end
    else
      chrs.unshift ch
      if @postproc and @preproc.nil? || @preproc.call(op, chrs)
        DOUT.printf(D_DETAIL, "op3: %s\n", op)
        @postproc.call(op, chrs)
        return ""
      else
        return nil
      end
    end
  end
end