John Meacham wrote:
On Thu, Apr 27, 2006 at 11:09:58AM +0100, Adrian Hey wrote:
What really frustrates me about all this is that AFAIK there are no significant technical or theoretical reasons why we can't get this safety (without resort to the unsafePerformIO hack). The only serious obstacle seems political, with this very strange but apparently widespread dogma about so called "global variables" being inherently evil, regardless of the circumstances or purpose for which they are used.
indeed. perhaps we just need to come up with a more functional name than 'global variables'. like 'universal monad' or 'world transformer', maybe 'augmented IO'. :)
I like "augmented IO", because this makes it clear that there is absolutely no difference between the existing IO monad which keeps track of global RealWorld state, and an augmented IO monad which keeps track of RealWorld + state of IORefs needed internally by different components of a software system. At the moment, there is a strange unnatural discrepancy between the fixed set of built-in privileged operations such as newUnique which are "allowed" to make use of global state and user defined operations which have to rely on a shaky hack in order to preserve natural abstraction barriers between components such as a user-defined Unique, Atom, and anything involving memoisation or device management etc. Regards, Brian.