Sometimes my Ruby code has enough parens, it might as well be Lisp

assigned_to_sites.rb

# find admin users assigned to a given set of sites
named_scope :assigned_to_sites, lambda { |site_ids|
  {
    :joins => :admin_user_site_assignments,
    :conditions => {
      :admin_user_site_assignments => {:site_id => site_ids}
    }
  }
}

in_booking_window.rb

def in_booking_window?
  (begin_booking_at.nil? or Time.now.utc >= begin_booking_at) and (end_booking_at.nil? or Time.now.utc <= end_booking_at)
end