We have seen that Lisp and ML include such imperative features as assignment and iteration. How important are these? What do languages like Haskell give up (conversely, what do they gain) by insisting...

We have seen that Lisp and ML include such imperative features as assignment and iteration. How important are these? What do languages like

Haskell give up (conversely, what do they gain) by insisting on a purely

functional programming style? In a similar vein, what do you think of attempts in several recent imperative languages (notably Python and C#—

see Sidebar 11.6) to facilitate functional programming with function constructors and unlimited extent?