在GHC.IO中,差异和预期用途有何用途ioToST和unsafeSTToIO定义？
-- ---------------------------------------------------------------------------
-- Coercions between IO and ST
-- | A monad transformer embedding strict state transformers in the 'IO'
-- monad. The 'RealWorld' parameter indicates that the internal state
-- used by the 'ST' computation is a special one supplied by the 'IO'
-- monad, and thus distinct from those used by invocations of 'runST'.
stToIO :: ST RealWorld a -> IO a
stToIO (ST m) = IO m
ioToST :: IO …