def slice_url(*args)
  params = args.last.is_a?(Hash) ? args.pop : {}
  slice_name, route_name = if args[0].is_a?(Symbol) && args[1].is_a?(Symbol)
    [args.shift, args.shift] # other slice identifier, route name
  elsif args[0].is_a?(Symbol)
    [slice.identifier_sym, args.shift] # self, route name
  else
    args.unshift(params)
    [slice.identifier_sym, :default] # self, default route
  end

  unless route = Merb::Slices.named_routes[slice_name][route_name]
    raise Merb::Router::GenerationError, "Named route not found: #{route_name}"
  end

  route.generate(args, params)
end