Should I add set nocount for functions? I've been reading about the benefits for all triggers and procedures having "set nocount on" implemented unless you make use of DONE_IN_PROC.

I have a scalar-valued function that is called from an update trigger to calculate the sum of values across multiple tables. 

Searching msdn and past articles, I haven't been able to find an explicit example of a function using set nocounton.

What is the impact on a function to include or exclude 'set nocount on'?
Is there a point or code smell in functions that should indicate the addition of set nocount on?
Functions cannot return data to a client so I can't think of any use of SET NOCOUNT ON. If you do try to add it a function you'll get an error. SQL Server considers it to cause a side effect:


  function_body
  
  Specifies that a series of Transact-SQL statements, which together do not produce a side effect such as modifying a table, define the value of the function.


For example, the follow code throws an error:

CREATE FUNCTION X_JRO_TEST() 
RETURNS INT
AS
BEGIN
SET NOCOUNT ON;
RETURN 1;
END;



  Msg 443, Level 16, State 15, Procedure X_JRO_TEST, Line 5
  
  Invalid use of a side-effecting operator 'SET OPTION ON' within a function.