2.1.893 Part 4 Section, Functions

a.   The standard does not use EBNF to write the productions for function-call.

Office writes the productions for function-call using the following EBNF:

   function-name,  "(",  argument-list,  ")"    ;
   predefined-function-name |
   user-defined-function-name ;
   "ABS"  |  "ACOS"  |  "ACOSH"
   |  ( any of the other functions defined in Predefined Function Definitions (“[ECMA-376] Part 4 §3.17.7; Predefined Function Definitions”))  ;
   name-reference ;
   argument,  {  comma,  argument  }  ;
   ","  ;
   [expression]  ;

b.   The standard states that a function is a named formula that takes zero or more arguments, performs an operation, and, optionally, returns a result.

In Office, a function always returns a result.