-- Portability : non-portable (requires universal quantification for runST)
--
-- This module presents an identical interface to "Control.Monad.ST",
-- Portability : non-portable (requires universal quantification for runST)
--
-- This module presents an identical interface to "Control.Monad.ST",
--- but the underlying implementation of the state thread is /lazy/ (in
--- the sense that (@_|_ >> a@ is not necessarily equal to @_|_@).
+-- except that the monad delays evaluation of state operations until
+-- a value depending on them is required.
--
-- It serves to keep the internal states of different invocations of
-- 'runST' separate from each other and from invocations of 'stToIO'.
--
-- It serves to keep the internal states of different invocations of
-- 'runST' separate from each other and from invocations of 'stToIO'.
newtype ST s a = ST (State s -> (a, State s))
data State s = S# (State# s)
newtype ST s a = ST (State s -> (a, State s))
data State s = S# (State# s)