Control.Monad.ST.Unsafe

This library provides support for strict state threads, as described in the PLDI '94 paper by John Launchbury and Simon Peyton Jones Lazy Functional State Threads.

Unsafe API.

Unsafe operations

unsafeInterleaveST :: ST s a -> ST s a

unsafeInterleaveST allows an ST computation to be deferred lazily. When passed a value of type ST a, the ST computation will only be performed when the value of the a is demanded.

unsafeDupableInterleaveST :: ST s a -> ST s a

unsafeDupableInterleaveST allows an ST computation to be deferred lazily. When passed a value of type ST a, the ST computation will only be performed when the value of the a is demanded.

The computation may be performed multiple times by different threads, possibly at the same time. To prevent this, use unsafeInterleaveST instead.

Since: 4.11

unsafeIOToST :: IO a -> ST s a

Convert an IO action to an ST action. This relies on IO and ST having the same representation modulo the constraint on the type of the state.

unsafeSTToIO :: ST s a -> IO a

Convert an ST action to an IO action. This relies on IO and ST having the same representation modulo the constraint on the type of the state.

For an example demonstrating why this is unsafe, see https://mail.haskell.org/pipermail/haskell-cafe/2009-April/060719.html