Hello Jeff, Thursday, February 7, 2008, 4:17:27 AM, you wrote:
logical place for mutable arrays. However, I don't understand the motivation for implementing it in IO. Were mutable arrays added to IO because it would be difficult to write code that does both IO and manipulates arrays otherwise?
yes. you can't perform separate ST actions in IO monad, you may call only entire computations with pure results - the same as you can do from pure code IO monad implements idea of sequencing actions and it is used ro "import" any actions written in other languages (C/C++ in most cases). ST monad is just the same internally but it was directive limited to only two types of actions - with variables and mutable arrays. this, together with some type tricks ensures that its results are referentially-transparent and therefore may be called from pure code -- Best regards, Bulat mailto:Bulat.Ziganshin@gmail.com