[Haskell-cafe] On the purity of Haskell

[Chris Smith]

On Fri, 2011-12-30 at 18:34 +0200, Artyom Kazak wrote:
> I wonder: can writing to memory be called a “computational effect”? If  
> yes, then every computation is impure. If no, then what’s the difference  
> between memory and hard drive?

The difference is that our operating systems draw an abstraction
boundary such that memory is private to a single program, while the hard
drive is shared between independent entities.  It's not the physical
distinction (which has long been blurred by virtual memory and caches
anyway), but the fact that they are on different sides of that
abstraction boundary.

-- 
Chris Smith