parse_weekday_list (Icalendar::RRule)

    # File lib/icalendar/parser.rb, line 78
        def parse_weekday_list(name, string)
          match = string.match(/;#{name}=(.*?)(;|$)/)
          if match
            match[1].split(",").map {|weekday|
              wd_match = weekday.match(/([+-]?\d*)(SU|MO|TU|WE|TH|FR|SA)/)
              Weekday.new(wd_match[2], wd_match[1])
              }
          else
            nil
          end
        end