[Haskell-cafe] On the purity of Haskell

[Donn Cave]

Quoth Gregg Reynolds <dev at mobileink.com>,
..
> A minor point maybe, but germane to the original post (I hope).

It isn't - I mean, I'm not really sure what your point is, but
the example really returns the same IO value, not just one of
the same type.

Consider an example with implementation:

   wint :: Int -> IO Int
   wint a = let s = show a in do
       putStr s
       return (length s)

Now the expression "wint 994" is a value of type IO Int, and
any instance of that expression is the same value - an action
is not the same as the action's result.  You can use this
value in pure Haskell expressions with confidence.

	Donn