Difference between revisions of "Unsafe functions"
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* type safety (<code>unsafeCoerce#</code>, <code>unsafePerformIO</code>), |
* type safety (<code>unsafeCoerce#</code>, <code>unsafePerformIO</code>), |
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| − | * [https://okmij.org/ftp/Haskell/index.html#lazyIO-not-True |
+ | * [https://okmij.org/ftp/Haskell/index.html#lazyIO-not-True equational reasoning] (<code>unsafeInterleaveIO</code>), |
| − | * or |
+ | * or [http://en.wikipedia.org/wiki/Parametricity parametricity] (<code>seq</code>). |
Their use (except in the case of <code>seq</code>) would require some |
Their use (except in the case of <code>seq</code>) would require some |
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Revision as of 05:57, 11 August 2022
A colleague [...] asked me today whether I know how to use unsafePerformIO safely. And I realized I have no idea.
There are a number of unsafe functions in the libraries.
unsafePerformIO :: IO a -> aunsafeInterleaveIO :: IO a -> IO aunsafeInterleaveST :: ST s a -> ST s aunsafeIOToST :: IO a -> ST s aunsafeIOToSTM :: IO a -> STM aunsafeFreeze,unsafeThawunsafeCoerce# :: a -> bseq :: a -> b -> b
Unsafe functions can break:
- type safety (
unsafeCoerce#,unsafePerformIO),
- equational reasoning (
unsafeInterleaveIO),
- or parametricity (
seq).
Their use (except in the case of seq) would require some
kind of assurance on the part of the programmer that what they're doing
is safe.
unsafe is also a keyword which can be used in a foreign import declaration.
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