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Within LTS Haskell 24.38 (ghc-9.10.3)
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mallocForeignPtrBytes :: Int -> IO (ForeignPtr a)base-compat Foreign.ForeignPtr.Safe.Compat This function is similar to mallocForeignPtr, except that the size of the memory required is given explicitly as a number of bytes.
newForeignPtr :: FinalizerPtr a -> Ptr a -> IO (ForeignPtr a)base-compat Foreign.ForeignPtr.Safe.Compat Turns a plain memory reference into a foreign pointer, and associates a finalizer with the reference. The finalizer will be executed after the last reference to the foreign object is dropped. There is no guarantee of promptness, however the finalizer will be executed before the program exits.
newForeignPtrEnv :: FinalizerEnvPtr env a -> Ptr env -> Ptr a -> IO (ForeignPtr a)base-compat Foreign.ForeignPtr.Safe.Compat This variant of newForeignPtr adds a finalizer that expects an environment in addition to the finalized pointer. The environment that will be passed to the finalizer is fixed by the second argument to newForeignPtrEnv.
newForeignPtr_ :: Ptr a -> IO (ForeignPtr a)base-compat Foreign.ForeignPtr.Safe.Compat Turns a plain memory reference into a foreign pointer that may be associated with finalizers by using addForeignPtrFinalizer.
touchForeignPtr :: ForeignPtr a -> IO ()base-compat Foreign.ForeignPtr.Safe.Compat This function ensures that the foreign object in question is alive at the given place in the sequence of IO actions. However, this comes with a significant caveat: the contract above does not hold if GHC can demonstrate that the code preceding touchForeignPtr diverges (e.g. by looping infinitely or throwing an exception). For this reason, you are strongly advised to use instead withForeignPtr where possible. Also, note that this function should not be used to express dependencies between finalizers on ForeignPtrs. For example, if the finalizer for a ForeignPtr F1 calls touchForeignPtr on a second ForeignPtr F2, then the only guarantee is that the finalizer for F2 is never started before the finalizer for F1. They might be started together if for example both F1 and F2 are otherwise unreachable, and in that case the scheduler might end up running the finalizer for F2 first. In general, it is not recommended to use finalizers on separate objects with ordering constraints between them. To express the ordering robustly requires explicit synchronisation using MVars between the finalizers, but even then the runtime sometimes runs multiple finalizers sequentially in a single thread (for performance reasons), so synchronisation between finalizers could result in artificial deadlock. Another alternative is to use explicit reference counting.
withForeignPtr :: ForeignPtr a -> (Ptr a -> IO b) -> IO bbase-compat Foreign.ForeignPtr.Safe.Compat This is a way to look at the pointer living inside a foreign object. This function takes a function which is applied to that pointer. The resulting IO action is then executed. The foreign object is kept alive at least during the whole action, even if it is not used directly inside. Note that it is not safe to return the pointer from the action and use it after the action completes. All uses of the pointer should be inside the withForeignPtr bracket. The reason for this unsafeness is the same as for unsafeForeignPtrToPtr below: the finalizer may run earlier than expected, because the compiler can only track usage of the ForeignPtr object, not a Ptr object made from it. This function is normally used for marshalling data to or from the object pointed to by the ForeignPtr, using the operations from the Storable class.
unsafeForeignPtrToPtr :: ForeignPtr a -> Ptr abase-compat Foreign.ForeignPtr.Unsafe.Compat This function extracts the pointer component of a foreign pointer. This is a potentially dangerous operations, as if the argument to unsafeForeignPtrToPtr is the last usage occurrence of the given foreign pointer, then its finalizer(s) will be run, which potentially invalidates the plain pointer just obtained. Hence, touchForeignPtr must be used wherever it has to be guaranteed that the pointer lives on - i.e., has another usage occurrence. To avoid subtle coding errors, hand written marshalling code should preferably use withForeignPtr rather than combinations of unsafeForeignPtrToPtr and touchForeignPtr. However, the latter routines are occasionally preferred in tool generated marshalling code.
unsafeDupablePerformIO :: IO a -> abase-compat System.IO.Unsafe.Compat This version of unsafePerformIO is more efficient because it omits the check that the IO is only being performed by a single thread. Hence, when you use unsafeDupablePerformIO, there is a possibility that the IO action may be performed multiple times (on a multiprocessor), and you should therefore ensure that it gives the same results each time. It may even happen that one of the duplicated IO actions is only run partially, and then interrupted in the middle without an exception being raised. Therefore, functions like bracket cannot be used safely within unsafeDupablePerformIO.
segmentBefore :: (a -> Bool) -> [a] -> [[a]]utility-ht Data.List.HT Split the list before each occurence of a leading character. Keep these characters. There is always a list for the part before the first leading character. It may be empty. See package non-empty for more precise result type.
>>> segmentBefore isUpper "AbcdXyz" ["","Abcd","Xyz"] >>> segmentBefore isUpper "kAbcdXYZ" ["k","Abcd","X","Y","Z"]
forAllPredicates $ \p xs -> concat (segmentBefore p xs) == xs
forAllPredicates $ \p xs -> length (filter p xs) == length (tail (segmentBefore p xs))
forAllPredicates $ \p -> all (p . head) . tail . segmentBefore p
forAllPredicates $ \p -> all (all (not . p) . tail) . tail . segmentBefore p
forAllPredicates $ \p x -> flip seq True . (!!100) . concat . segmentBefore p . cycle . (x:)
segmentBeforeJust :: (a -> Maybe b) -> [a] -> ([a], [(b, [a])])utility-ht Data.List.HT >>> segmentBeforeJust (\c -> toMaybe (isLetter c) (toUpper c)) "123a5345b---" ("123",[('A',"5345"),('B',"---")])