Something I've always wondered about Haskell. Given referential transparency, purity, etc shouldn't it be possible for the Haskell compiler to choose whether to evaluate something in an eager or lazy fashion depending on performance heuristics under the covers? You have to make sure you don't ever accidentally do that with an infinite list but it seems that there ought to be lots of scope for optimization and speeding up code written in a straightforward fashion. Possibly also turning lists into arrays secretly too if it can be proven to produce the same result.
The point of lazy evaluation is to evaluate something only when you really need it. Not to auto-adjust the system performance wise. You can force eager evaluation in places where you want it evaluated sooner.
Personally, I think consistency is more important here because it leads to better predictability. If you don't know whether the compiler assigns something to be evaluated lazily or eagerly that could lead to a lot of nasty debugging issues.
