Monad composition

[John Hughes]

	Andre W B Furtado wrote:
	>Well, it's also possible to interchange data between these two monads by:
	>
	>unsafeIOToST :: IO a -> ST s a
	>stToIO :: ST s a -> IO a
	>
	>Can anyone tell the possible problems related to
	>unsafeIOToST?
	>^^^^^^

	Probably in the same manner as with unsafePerformIO:
	it can break referential transparency.

Indeed,

  unsafePerformIO m = runST (unsafeIOToST m)

so they're just as unsafe as each other.

John Hughes