2.76¶

; As a large system with generic operations evolves, new types of data objects or 
; new operations may be needed. For each of the three strategies — generic operations
; with explicit dispatch, data-directed style, and message-passing-style — describe 
; the changes that must be made to a system in order to add new types or new 
; operations. Which organization would be most appropriate for a system in which 
; new types must often be added? Which would be most appropriate for a system in 
; which new operations must often be added?

; Ans
; * Use data-directed approach when new operations are added
; * Use message-passing approach when new types are added