# File lib/rufus/treechecker.rb, line 525
    def do_check(sexp)

      continue = @set.check(sexp)

      return unless continue
        # found an accepted pattern, no need to dive into it

      return unless sexp.is_a?(Array)
        # check over, seems fine...

      #
      # check children

      sexp.each { |c| do_check(c) }
    end