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  1. (<$>) :: Functor f => (a -> b) -> f a -> f b

    ihaskell IHaskellPrelude

    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)

  2. pattern (:$$:) :: () => ErrorMessage -> ErrorMessage -> ErrorMessage

    incipit-base Incipit.Base

    Stack two pieces of error message on top of each other.

  3. (<$) :: Functor f => a -> f b -> f a

    incipit-base Incipit.Base

    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

  4. (<$!>) :: Monad m => (a -> b) -> m a -> m b

    incipit-base Incipit.Base

    Strict version of <$>.

  5. (<$>) :: Functor f => (a -> b) -> f a -> f b

    incipit-base Incipit.Base

    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)

  6. (>$) :: Contravariant f => b -> f b -> f a

    incipit-base Incipit.Base

    Replace all locations in the output with the same value. The default definition is contramap . const, but this may be overridden with a more efficient version.

  7. (>$<) :: Contravariant f => (a -> b) -> f b -> f a

    incipit-base Incipit.Base

    This is an infix alias for contramap.

  8. (|$|) :: Semigroup t => (a -> b) -> a -> PerfT IO t b

    perf Perf.Types

    lift a pure, unnamed function application to PerfT

  9. (***$) :: Profunctor p => (b -> c) -> p a b -> p a c

    product-profunctors Data.Profunctor.Product

    ***$ is the generalisation of Functor's <$>. ***$ = rmap, just like <$> = fmap. (You probably won't need to use this. <$> should be sufficient.) Since 0.11.1.0: Generalised to work on arbitrary Profunctors.

  10. (***$) :: Profunctor p => (b -> c) -> p a b -> p a c

    product-profunctors Data.Profunctor.Product

    ***$ is the generalisation of Functor's <$>. ***$ = rmap, just like <$> = fmap. (You probably won't need to use this. <$> should be sufficient.) Since 0.11.1.0: Generalised to work on arbitrary Profunctors.

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