Ramin wrote:
Well, in C/C++, and most any other imperative languages (as you probably know) is O(1) for both reading and updating arrays. Until Haskell can do this, I don't think Haskell is a viable option for operating system design, computer graphics, or embedded applications.
There are two issues here, which I think were unnecessarily tangled together in your original post. First: you proposed arrays whose size is known and accesses checked at compile-time. Second: you proposed making arrays mutable so as to recover the expected time bounds for operations. The first is possible, but considerably more complex that your original post made it sound. The second, though, is already there in Haskell as it stands. Just use STArray, for example. The big difference is that with STArray, the side effects of your code, and the fact that the original copy of the array is destroyed, are acknowledged by the type system. You tried to give changeArrayFunc a type of a^10 -> a^10: a type that implies it computes a new value, but leaves the original array alone. Unless it does some analysis, that could be arbitrarily complex in general, to prove I never use the original array again, the compiler can *not* generate destructive code in this case. The ST monad *is* the general answer to this problem, so you should just use STArray, and you get what you want. -- Chris Smith