[Haskell-cafe] On the purity of Haskell /Random generators

[Steve Horne]

On 29/12/2011 20:39, Jerzy Karczmarczuk wrote:
> Still, I dont understand what does S.H.  mean by a "perfectly good 
> pure generator".
> Tell more please (unless you just mean a stream, say:
>
Probably bad wording, to be honest. I only meant that there's random 
number handling support in the Haskell library and, and least judging by 
type signatures, it's pure functional code with no hint of the IO monad.

AFAIK there's no hidden unsafePerformIO sneaking any entropy in behind 
the scenes. Even if there was, it might be a legitimate reason for 
unsafePerformIO - random numbers are in principle non-deterministic, not 
determined by the current state of the outside world and 
which-you-evaluate-first should be irrelevant. If you have a quantum 
genuine-random-numbers gadget, the IO monad might be considered 
redundant for functions that get values from it - though it still isn't 
referentially transparent as it returns a different value each time even 
with the same parameters.

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