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Within LTS Haskell 24.41 (ghc-9.10.3)
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(
<$ ) :: Functor f => a -> f b -> f abasement Basement.Imports Replace all locations in the input with the same value. The default definition is fmap . const, but this may be overridden with a more efficient version.
Examples
Perform a computation with Maybe and replace the result with a constant value if it is Just:>>> 'a' <$ Just 2 Just 'a' >>> 'a' <$ Nothing Nothing
(
<$> ) :: Functor f => (a -> b) -> f a -> f bbasement Basement.Imports An infix synonym for fmap. The name of this operator is an allusion to $. Note the similarities between their types:
($) :: (a -> b) -> a -> b (<$>) :: Functor f => (a -> b) -> f a -> f b
Whereas $ is function application, <$> is function application lifted over a Functor.Examples
Convert from a Maybe Int to a Maybe String using show:>>> show <$> Nothing Nothing
>>> show <$> Just 3 Just "3"
Convert from an Either Int Int to an Either Int String using show:>>> show <$> Left 17 Left 17
>>> show <$> Right 17 Right "17"
Double each element of a list:>>> (*2) <$> [1,2,3] [2,4,6]
Apply even to the second element of a pair:>>> even <$> (2,2) (2,True)
(
>$ ) :: forall b (m :: Type -> Type) a . b -> LogAction m b -> LogAction m aco-log-core Colog.Core.Action This combinator is >$ from contravariant functor. Replaces all locations in the output with the same value. The default definition is contramap . const, so this is a more efficient version.
>>> "Hello?" &> ("OUT OF SERVICE" >$ logStringStdout) OUT OF SERVICE >>> ("OUT OF SERVICE" >$ logStringStdout) <& 42 OUT OF SERVICE(
>$< ) :: forall a b (m :: Type -> Type) . (a -> b) -> LogAction m b -> LogAction m aco-log-core Colog.Core.Action Operator version of cmap.
>>> 1 &> (show >$< logStringStdout) 1
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singletons-base Control.Applicative.Singletons No documentation available.
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singletons-base Control.Applicative.Singletons No documentation available.
data (a6989586621679356661 :: f a)
*>@#@$$ (b1 :: TyFun f b f b)singletons-base Control.Applicative.Singletons No documentation available.
type family (a6989586621679356661 :: f a)
*>@#@$$$ (a6989586621679356662 :: f b) :: f bsingletons-base Control.Applicative.Singletons No documentation available.
type family (arg :: a)
<$ (arg1 :: f b) :: f asingletons-base Control.Applicative.Singletons No documentation available.
type family (a1 :: a ~> b)
<$> (a2 :: f a) :: f bsingletons-base Control.Applicative.Singletons No documentation available.