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

    ghc-internal GHC.Internal.Data.Functor

    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)

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

    ghc-internal GHC.Internal.Data.List

    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]

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

    ghc-internal GHC.Internal.Data.OldList

    Map a function returning a list over a list and concatenate the results. concatMap can be seen as the composition of concat and map. 

    concatMap f xs == (concat . map f) xs

    Examples

    >>> concatMap (\i -> [-i,i]) []
[]

    >>> concatMap (\i -> [-i, i]) [1, 2, 3]
[-1,1,-2,2,-3,3]

    >>> concatMap ('replicate' 3) [0, 2, 4]
[0,0,0,2,2,2,4,4,4]

  4. fmapDefault :: Traversable t => (a -> b) -> t a -> t b

    ghc-internal GHC.Internal.Data.Traversable

    This function may be used as a value for fmap in a Functor instance, provided that traverse is defined. (Using fmapDefault with a Traversable instance defined only by sequenceA will result in infinite recursion.) 

    fmapDefault f ≡ runIdentity . traverse (Identity . f)

  5. foldMapDefault :: (Traversable t, Monoid m) => (a -> m) -> t a -> m

    ghc-internal GHC.Internal.Data.Traversable

    This function may be used as a value for foldMap in a Foldable instance. 

    foldMapDefault f ≡ getConst . traverse (Const . f)

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

    ghc-internal GHC.Internal.List

    Map a function returning a list over a list and concatenate the results. concatMap can be seen as the composition of concat and map. 

    concatMap f xs == (concat . map f) xs

    Examples

    >>> concatMap (\i -> [-i,i]) []
[]

    >>> concatMap (\i -> [-i, i]) [1, 2, 3]
[-1,1,-2,2,-3,3]

    >>> concatMap ('replicate' 3) [0, 2, 4]
[0,0,0,2,2,2,4,4,4]

  7. contextGetFontMap :: (HasCallStack, MonadIO m, IsContext a) => a -> m (Maybe FontMap)

    gi-pango GI.Pango.Objects.Context

    Gets the PangoFontMap used to look up fonts for this context. Since: 1.6

  8. contextSetFontMap :: (HasCallStack, MonadIO m, IsContext a, IsFontMap b) => a -> Maybe b -> m ()

    gi-pango GI.Pango.Objects.Context

    Sets the font map to be searched when fonts are looked-up in this context. This is only for internal use by Pango backends, a PangoContext obtained via one of the recommended methods should already have a suitable font map.

  9. fontGetFontMap :: (HasCallStack, MonadIO m, IsFont a) => Maybe a -> m (Maybe FontMap)

    gi-pango GI.Pango.Objects.Font

    Gets the font map for which the font was created. Note that the font maintains a *weak* reference to the font map, so if all references to font map are dropped, the font map will be finalized even if there are fonts created with the font map that are still alive. In that case this function will return Nothing. It is the responsibility of the user to ensure that the font map is kept alive. In most uses this is not an issue as a PangoContext holds a reference to the font map. Since: 1.10

  10. module GI.Pango.Objects.FontMap

    A PangoFontMap represents the set of fonts available for a particular rendering system. This is a virtual object with implementations being specific to particular rendering systems.

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