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  1. concatMap :: Foldable t => (a -> [b]) -> t a -> [b]

    ghc-lib-parser GHC.Prelude.Basic

    Map a function over all the elements of a container and concatenate the resulting lists.

    Examples

    Basic usage: 
    >>> concatMap (take 3) [[1..], [10..], [100..], [1000..]]
[1,2,3,10,11,12,100,101,102,1000,1001,1002]

    >>> concatMap (take 3) (Just [1..])
[1,2,3]

  2. fmap :: Functor f => (a -> b) -> f a -> f b

    ghc-lib-parser GHC.Prelude.Basic

    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)

  3. foldMap :: (Foldable t, Monoid m) => (a -> m) -> t a -> m

    ghc-lib-parser GHC.Prelude.Basic

    Map each element of the structure into a monoid, and combine the results with (<>). This fold is right-associative and lazy in the accumulator. For strict left-associative folds consider foldMap' instead.

    Examples

    Basic usage: 
    >>> foldMap Sum [1, 3, 5]
Sum {getSum = 9}

    >>> foldMap Product [1, 3, 5]
Product {getProduct = 15}

    >>> foldMap (replicate 3) [1, 2, 3]
[1,1,1,2,2,2,3,3,3]
    When a Monoid's (<>) is lazy in its second argument, foldMap can return a result even from an unbounded structure. For example, lazy accumulation enables Data.ByteString.Builder to efficiently serialise large data structures and produce the output incrementally: 
    >>> import qualified Data.ByteString.Lazy as L

>>> import qualified Data.ByteString.Builder as B

>>> let bld :: Int -> B.Builder; bld i = B.intDec i <> B.word8 0x20

>>> let lbs = B.toLazyByteString $ foldMap bld [0..]

>>> L.take 64 lbs
"0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24"

  4. gconstmap :: (Generic1 f, Functor (Rep1 f)) => a -> f b -> f a

    generic-data Generic.Data.Internal.Prelude

    Generic (<$). See also gfmap.

  5. gfmap :: (Generic1 f, Functor (Rep1 f)) => (a -> b) -> f a -> f b

    generic-data Generic.Data.Internal.Prelude

    Generic fmap. 

    instance Functor MyTypeF where
fmap = gfmap

  6. gfoldMap :: (Generic1 f, Foldable (Rep1 f), Monoid m) => (a -> m) -> f a -> m

    generic-data Generic.Data.Internal.Prelude

    Deprecated: This definition has been replaced with gfoldMap.

  7. gmappend :: (Generic a, Semigroup (Rep a ())) => a -> a -> a

    generic-data Generic.Data.Internal.Prelude

    Generic (<>) (or mappend). 

    instance Semigroup MyType where
(<>) = gmappend
    See also gmempty.

  8. gmappend' :: (Generic a, Monoid (Rep a ())) => a -> a -> a

    generic-data Generic.Data.Internal.Prelude

    Generic (<>) (or mappend). The difference from gmappend is the Monoid constraint instead of Semigroup, for older versions of base where Semigroup is not a superclass of Monoid.

  9. concatMap :: (a -> [b]) -> [a] -> [b]

    prelude-compat Prelude2010

    No documentation available.

  10. fmap :: Functor f => (a -> b) -> f a -> f b

    prelude-compat Prelude2010

    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)

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