# File lib/scrubyt/core/scraping/result_indexer.rb, line 18
    def select_indices_to_extract(ary)
      return ary if @indices_to_extract == nil
      to_keep = []
      @indices_to_extract.each {|e|
        if e.is_a? Symbol
          case e
          when :first
            to_keep << 0
          when :last
            to_keep << ary.size-1
          when :all_but_last
           (0..ary.size-2).each {|i| to_keep << i} 
          when :all_but_first
           (1..ary.size-1).each {|i| to_keep << i} 
          when :every_even
           (0..ary.size).each {|i| to_keep << i if (i % 2 == 1)}
          when :every_odd
           (0..ary.size).each {|i| to_keep << i if (i % 2 == 0)}
          when :every_second
           (0..ary.size).each {|i| to_keep << i if (i % 2 == 0)}
          when :every_third
           (0..ary.size).each {|i| to_keep << i if (i % 3 == 0)}
          when :every_fourth
           (0..ary.size).each {|i| to_keep << i if (i % 4 == 0)}
          end
        end
      }
      @indices_to_extract.each {|i| to_keep << i if !i.is_a? Symbol}
      to_keep.sort!
      ary.reject! {|e| !to_keep.include? ary.index(e)}
      ary
    end