[Haskell-cafe] Maybe and partial functions

The Maybe construction is very useful for explicitly handling circumstances where the function cannot produce a sensible answer. But how far should this notion be taken? When you're writing a function which you realise may not produce what you want, in what circumstances would you use a Maybe, and when would you just throw an error? I'm wondering both in terms of good engineering practise and also for correctness. Should elementary partial functions like

5 `div` 0

or

head []

return Nothing? I guess it's a bit of a silly suggestion, but it helps to highlight why we use Maybe in the first place. So --- where's the cutoff point in your code? Cheers, D. -- Dougal Stanton