[frubar]

>In many languages: arr[idx] = nevalue

The thing you have to keep in mind is that this kind of naked mutation is probably the main source of bugs in programming today. One of the main advantages of OO was that it demarcated which functions could modify a "global" variable. But if I get a weird value in one of my fields, I still can't trivially tell how it got there, I can only narrow down to methods of the class (and possibly the inheritance tree, depending on variable visibility).

Due to that, there is more ceremony in modifying things in Haskell. The language works best if you write most of your code in a way that doesn't mutate anything and then limit mutation to a small area using the advanced techniques developed in the language. But doing all this requires a pretty substantial investment so you probably need something to convince you that the end will be worth it before you start. I don't know what you tell you, what got me interested was something like:

> fibs = 1 : 1 : zipWith (+) fibs (tail fibs)

and

> max = head . sort

but I understand that's not going to motivate most people to completely change how they approach programming as a discipline.