Safe Haskell	None
Language	Haskell2010

Defaultable.Map.Generalized

Contents

Description

This module exports an API that is similar to Defaultable.Map, except the utilities have been generalized further to work with any Map-like type.

The only utility that cannot be generalized in this way is lookup, so that is the only function missing from this module. Other than the missing lookup function, this module is a drop-in replacement for the Defaultable.Map module.

Also, keep in mind that these generalized utilities may have worse type inference (especially you omit type annotations) and in some cases might also be more inefficient. If this is an issue for you then you'll need to create your own local module specializing these utilities to your Map-like type of interest.

Synopsis

data Defaultable map value = Defaultable (map value) (Maybe value)
fromMap :: map value -> Defaultable map value
singleton :: IsList (map value) => Item (map value) -> Defaultable map value
fromList :: IsList (map value) => [Item (map value)] -> Defaultable map value
insert :: (IsList (map value), Apply map, forall a. Monoid (map a)) => Item (map value) -> Defaultable map value -> Defaultable map value
withDefault :: (Apply map, forall a. Monoid (map a)) => Defaultable map value -> value -> Defaultable map value
toMap :: Defaultable map value -> map value
toDefault :: Defaultable map value -> Maybe value

Documentation

data Defaultable map value Source #

A Defaultable type is a Map-like type that is extended with an optional default value. This default value can be used as a fallback if a lookup into the Map-like type does not find a matching key.

The type variables are:

map: The Map-like type to wrap (typically including the type of key, but not the type of the value)
value The type of each value stored in the Map-like type

For example, you will typically have a type like Defaultable (Map key) value or Defaultable IntMap value.

You can build a Defaultable value using:

empty - The empty Defaultable has no keys and no default value
pure - A Defaultable with a default value but no keys
fromMap / fromList / singleton - Convenient construction functions
The Defaultable constructor

You can transform and combine Defaultable values using:

(<|>) - Concatenate two Defaultable values, preferring keys and defaults from the left one
do notation, if you enable ApplicativeDo
withDefault - To extend a Defaultable value with a default value

You can query a Defaultable value using:

lookup
toMap / toDefault

Note that the Applicative instance for this type is only valid for map type constructors that satisfy the following extra law:

Given:

• mf :: map (a -> b)
• mx :: map a
• kf :: (a -> b) -> c
• kx :: a -> c

  (mf <.> mx) <> fmap kf mf <> fmap kx mx
= (mf <.> mx) <> fmap kx mx <> fmap kf mf

… where map is the first type parameter that implements Apply and Monoid.

The intuition here is if that map is a Map-like type then we can think of those three expressions as having a set of keys associated with them, such that:

Given:

• keys :: map a -> Set key

keys (mf <.> mx) = keys (fmap kf mf) `intersection` keys (fmap kx mx)

So normally the following equality would not be true:

  fmap kf mf <> fmap kx mx
= fmap kx mx <> fmap kf mf

… because the result would change if there was a key collision. Then the order in which we union (<>) the two maps would change the result.

However, if you union yet another map (mf <.> mx) that shadows the colliding keys then result remains the same.

Constructors

Defaultable
Fields (map value) The underlying `Map`-like type (Maybe value) An optional default value to return if a key is missing

Instances

Instances details

Functor map => Functor (Defaultable map) Source #
Instance details Defined in Defaultable.Map Methods fmap :: (a -> b) -> Defaultable map a -> Defaultable map b # (<$) :: a -> Defaultable map b -> Defaultable map a #
(Apply map, forall a. Monoid (map a)) => Applicative (Defaultable map) Source #
Instance details Defined in Defaultable.Map Methods pure :: a -> Defaultable map a # (<>) :: Defaultable map (a -> b) -> Defaultable map a -> Defaultable map b # liftA2 :: (a -> b -> c) -> Defaultable map a -> Defaultable map b -> Defaultable map c # (>) :: Defaultable map a -> Defaultable map b -> Defaultable map b # (<*) :: Defaultable map a -> Defaultable map b -> Defaultable map a #
Foldable map => Foldable (Defaultable map) Source #
Instance details Defined in Defaultable.Map Methods fold :: Monoid m => Defaultable map m -> m # foldMap :: Monoid m => (a -> m) -> Defaultable map a -> m # foldMap' :: Monoid m => (a -> m) -> Defaultable map a -> m # foldr :: (a -> b -> b) -> b -> Defaultable map a -> b # foldr' :: (a -> b -> b) -> b -> Defaultable map a -> b # foldl :: (b -> a -> b) -> b -> Defaultable map a -> b # foldl' :: (b -> a -> b) -> b -> Defaultable map a -> b # foldr1 :: (a -> a -> a) -> Defaultable map a -> a # foldl1 :: (a -> a -> a) -> Defaultable map a -> a # toList :: Defaultable map a -> [a] # null :: Defaultable map a -> Bool # length :: Defaultable map a -> Int # elem :: Eq a => a -> Defaultable map a -> Bool # maximum :: Ord a => Defaultable map a -> a # minimum :: Ord a => Defaultable map a -> a # sum :: Num a => Defaultable map a -> a # product :: Num a => Defaultable map a -> a #
Traversable map => Traversable (Defaultable map) Source #
Instance details Defined in Defaultable.Map Methods traverse :: Applicative f => (a -> f b) -> Defaultable map a -> f (Defaultable map b) # sequenceA :: Applicative f => Defaultable map (f a) -> f (Defaultable map a) # mapM :: Monad m => (a -> m b) -> Defaultable map a -> m (Defaultable map b) # sequence :: Monad m => Defaultable map (m a) -> m (Defaultable map a) #
(Apply map, forall a. Monoid (map a)) => Alternative (Defaultable map) Source #
Instance details Defined in Defaultable.Map Methods empty :: Defaultable map a # (<\|>) :: Defaultable map a -> Defaultable map a -> Defaultable map a # some :: Defaultable map a -> Defaultable map [a] # many :: Defaultable map a -> Defaultable map [a] #
(Apply map, forall a. Monoid (map a)) => Alt (Defaultable map) Source #
Instance details Defined in Defaultable.Map Methods (<!>) :: Defaultable map a -> Defaultable map a -> Defaultable map a # some :: Applicative (Defaultable map) => Defaultable map a -> Defaultable map [a] # many :: Applicative (Defaultable map) => Defaultable map a -> Defaultable map [a] #
(Apply map, forall a. Monoid (map a)) => Apply (Defaultable map) Source #
Instance details Defined in Defaultable.Map Methods (<.>) :: Defaultable map (a -> b) -> Defaultable map a -> Defaultable map b # (.>) :: Defaultable map a -> Defaultable map b -> Defaultable map b # (<.) :: Defaultable map a -> Defaultable map b -> Defaultable map a # liftF2 :: (a -> b -> c) -> Defaultable map a -> Defaultable map b -> Defaultable map c #
Generic1 (Defaultable map :: Type -> Type) Source #
Instance details Defined in Defaultable.Map Associated Types type Rep1 (Defaultable map) :: k -> Type # Methods from1 :: forall (a :: k). Defaultable map a -> Rep1 (Defaultable map) a # to1 :: forall (a :: k). Rep1 (Defaultable map) a -> Defaultable map a #
(Eq value, Eq (map value)) => Eq (Defaultable map value) Source #
Instance details Defined in Defaultable.Map Methods (==) :: Defaultable map value -> Defaultable map value -> Bool # (/=) :: Defaultable map value -> Defaultable map value -> Bool #
(Typeable map, Data value, Data (map value)) => Data (Defaultable map value) Source #
Instance details Defined in Defaultable.Map Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Defaultable map value -> c (Defaultable map value) # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c (Defaultable map value) # toConstr :: Defaultable map value -> Constr # dataTypeOf :: Defaultable map value -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c (Defaultable map value)) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c (Defaultable map value)) # gmapT :: (forall b. Data b => b -> b) -> Defaultable map value -> Defaultable map value # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Defaultable map value -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Defaultable map value -> r # gmapQ :: (forall d. Data d => d -> u) -> Defaultable map value -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Defaultable map value -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Defaultable map value -> m (Defaultable map value) # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Defaultable map value -> m (Defaultable map value) # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Defaultable map value -> m (Defaultable map value) #
(Ord value, Ord (map value)) => Ord (Defaultable map value) Source #
Instance details Defined in Defaultable.Map Methods compare :: Defaultable map value -> Defaultable map value -> Ordering # (<) :: Defaultable map value -> Defaultable map value -> Bool # (<=) :: Defaultable map value -> Defaultable map value -> Bool # (>) :: Defaultable map value -> Defaultable map value -> Bool # (>=) :: Defaultable map value -> Defaultable map value -> Bool # max :: Defaultable map value -> Defaultable map value -> Defaultable map value # min :: Defaultable map value -> Defaultable map value -> Defaultable map value #
(Show value, Show (map value)) => Show (Defaultable map value) Source #
Instance details Defined in Defaultable.Map Methods showsPrec :: Int -> Defaultable map value -> ShowS # show :: Defaultable map value -> String # showList :: [Defaultable map value] -> ShowS #
Generic (Defaultable map value) Source #
Instance details Defined in Defaultable.Map Associated Types type Rep (Defaultable map value) :: Type -> Type # Methods from :: Defaultable map value -> Rep (Defaultable map value) x # to :: Rep (Defaultable map value) x -> Defaultable map value #
(Apply map, forall a. Monoid (map a), Semigroup value) => Semigroup (Defaultable map value) Source #	Not the same as the `Semigroup` instance for the underlying `map` type
Instance details Defined in Defaultable.Map Methods (<>) :: Defaultable map value -> Defaultable map value -> Defaultable map value # sconcat :: NonEmpty (Defaultable map value) -> Defaultable map value # stimes :: Integral b => b -> Defaultable map value -> Defaultable map value #
(Apply map, forall a. Monoid (map a), Monoid value) => Monoid (Defaultable map value) Source #	Not the same as the `Monoid` instance for the underlying `map` type
Instance details Defined in Defaultable.Map Methods mempty :: Defaultable map value # mappend :: Defaultable map value -> Defaultable map value -> Defaultable map value # mconcat :: [Defaultable map value] -> Defaultable map value #
(NFData value, NFData (map value)) => NFData (Defaultable map value) Source #
Instance details Defined in Defaultable.Map Methods rnf :: Defaultable map value -> () #
type Rep1 (Defaultable map :: Type -> Type) Source #
Instance details Defined in Defaultable.Map type Rep1 (Defaultable map :: Type -> Type) = D1 ('MetaData "Defaultable" "Defaultable.Map" "defaultable-map-1.0.2-inplace" 'False) (C1 ('MetaCons "Defaultable" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec1 map) :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec1 Maybe)))
type Rep (Defaultable map value) Source #
Instance details Defined in Defaultable.Map type Rep (Defaultable map value) = D1 ('MetaData "Defaultable" "Defaultable.Map" "defaultable-map-1.0.2-inplace" 'False) (C1 ('MetaCons "Defaultable" 'PrefixI 'False) (S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (map value)) :*: S1 ('MetaSel ('Nothing :: Maybe Symbol) 'NoSourceUnpackedness 'NoSourceStrictness 'DecidedLazy) (Rec0 (Maybe value))))

Construction

fromMap :: map value -> Defaultable map value Source #

Generalized version of fromMap

singleton :: IsList (map value) => Item (map value) -> Defaultable map value Source #

Generalized version of singleton

fromList :: IsList (map value) => [Item (map value)] -> Defaultable map value Source #

Generalized version of fromList

insert Source #

Arguments

:: (IsList (map value), Apply map, forall a. Monoid (map a))
=> Item (map value)
-> Defaultable map value
-> Defaultable map value

Generalized version of insert

withDefault Source #

Arguments

:: (Apply map, forall a. Monoid (map a))
=> Defaultable map value
-> value
-> Defaultable map value

Generalized version of withDefault

Query

toMap :: Defaultable map value -> map value Source #

Generalized version of toMap

toDefault :: Defaultable map value -> Maybe value Source #

Generalized version of toDefault