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reallyUnsafeLiftMapIO :: forall a b (es :: [Effect]) . (IO a -> IO b) -> Eff es a -> Eff es beffectful-core Effectful.Dispatch.Static.Unsafe Utility for lifting IO computations of type
IO a -> IO b
toEff es a -> Eff es b
This function is really unsafe because:- It can be used to introduce arbitrary IO actions into pure Eff computations.
- The IO computation must run its argument in a way that's perceived as sequential to the outside observer, e.g. in the same thread or in a worker thread that finishes before the argument is run again.
reallyUnsafeLiftMapIO :: forall a b (es :: [Effect]) . (IO a -> IO b) -> Eff es a -> Eff es beffectful-core Effectful.Internal.Monad Utility for lifting IO computations of type
IO a -> IO b
toEff es a -> Eff es b
This function is really unsafe because:- It can be used to introduce arbitrary IO actions into pure Eff computations.
- The IO computation must run its argument in a way that's perceived as sequential to the outside observer, e.g. in the same thread or in a worker thread that finishes before the argument is run again.
bimap :: Bifunctor p => (a -> b) -> (c -> d) -> p a c -> p b dfoundation Foundation Map over both arguments at the same time.
bimap f g ≡ first f . second g
Examples
>>> bimap toUpper (+1) ('j', 3) ('J',4)>>> bimap toUpper (+1) (Left 'j') Left 'J'
>>> bimap toUpper (+1) (Right 3) Right 4
fmap :: Functor f => (a -> b) -> f a -> f bfoundation Foundation fmap is used to apply a function of type (a -> b) to a value of type f a, where f is a functor, to produce a value of type f b. Note that for any type constructor with more than one parameter (e.g., Either), only the last type parameter can be modified with fmap (e.g., b in `Either a b`). Some type constructors with two parameters or more have a Bifunctor instance that allows both the last and the penultimate parameters to be mapped over.
Examples
Convert from a Maybe Int to a Maybe String using show:>>> fmap show Nothing Nothing >>> fmap show (Just 3) Just "3"
Convert from an Either Int Int to an Either Int String using show:>>> fmap show (Left 17) Left 17 >>> fmap show (Right 17) Right "17"
Double each element of a list:>>> fmap (*2) [1,2,3] [2,4,6]
Apply even to the second element of a pair:>>> fmap even (2,2) (2,True)
It may seem surprising that the function is only applied to the last element of the tuple compared to the list example above which applies it to every element in the list. To understand, remember that tuples are type constructors with multiple type parameters: a tuple of 3 elements (a,b,c) can also be written (,,) a b c and its Functor instance is defined for Functor ((,,) a b) (i.e., only the third parameter is free to be mapped over with fmap). It explains why fmap can be used with tuples containing values of different types as in the following example:>>> fmap even ("hello", 1.0, 4) ("hello",1.0,True)-
foundation Foundation.Array No documentation available.
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foundation Foundation.Array No documentation available.
imap :: InnerFunctor c => (Element c -> Element c) -> c -> cfoundation Foundation.Collection No documentation available.
nonEmptyFmap :: Functor f => (a -> b) -> NonEmpty (f a) -> NonEmpty (f b)foundation Foundation.Collection No documentation available.
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Note that the memory mapping is handled by the system, not at the haskell level. The system can modify the content of the memory as any moment under your feet. It also have the limitation of your system, no emulation or nice handling of all those corners cases is attempted here. for example mapping a large file (> 4G), on a 32 bits system is likely to just fail or returns inconsistent result. In doubt, use readFile or other simple routine that brings the content of the file in IO.
fileMapRead :: FilePath -> IO (UArray Word8)foundation Foundation.IO.FileMap Map in memory the whole content of a file. Once the array goes out of scope, the memory get (eventually) unmap