Rails 3 scope for select model depend on tags. Include selecting more tags ( && or || for them)

gistfile1.rb

  scope :tagged_with, lambda { |tags, match_all = false|
    tag_array = tags.is_a?(Array) ? TagList.new(tags) : TagList.from(tags)
    where_operator = match_all ? :& : :|
    where_conditions = tag_array.collect {|name| {:tags => :name =~ name} }
    where_sql = where_conditions.inject(&where_operator)
    select("DISTINCT prints.*").joins(:tags).where(where_sql)
  }