Container.Class

Reimagined approach for Foldable type hierarchy. Forbids usages of length function and similar over Maybe and other potentially unsafe data types. It was proposed to use -XTypeApplication for such cases. But this approach is not robust enough because programmers are human and can easily forget to do this. For discussion see this topic: Suggest explicit type application for Foldable length and friends

Foldable-like classes and methods

type family Element t

Type of element for some container. Implemented as a type family because some containers are monomorphic over element type (like Text, IntSet, etc.) so we can't implement nice interface using old higher-kinded types approach.

Instances

type Element ByteString

type Element ByteString = Word8

type Element ByteString

type Element ByteString = Word8

type Element IntSet

type Element IntSet = Int

type Element Text

type Element Text = Char

type Element Text

type Element Text = Char

type Element (f a)

type Element (f a) = a

type Element (WrappedList f a)

type Element (WrappedList f a) = a

class ToList t where

Type class for data types that can be converted to List. Fully compatible with Foldable. Contains very small and safe subset of Foldable functions.

You can define Tolist by just defining toList function. But the following law should be met:

null ≡ null . toList

Minimal complete definition

toList

Methods

toList :: t -> [Element t]

Convert container to list of elements.

>>> toList (Just True)
[True]
>>> toList @Text "aba"
"aba"
>>> :t toList @Text "aba"
toList @Text "aba" :: [Char]

null :: t -> Bool

Checks whether container is empty.

>>> null @Text ""
True
>>> null @Text "aba"
False

Instances

ToList ByteString

Methods

toList :: ByteString -> [Element ByteString]

null :: ByteString -> Bool

ToList ByteString

Methods

toList :: ByteString -> [Element ByteString]

null :: ByteString -> Bool

ToList IntSet

Methods

toList :: IntSet -> [Element IntSet]

null :: IntSet -> Bool

ToList Text

Methods

toList :: Text -> [Element Text]

null :: Text -> Bool

ToList Text

Methods

toList :: Text -> [Element Text]

null :: Text -> Bool

Foldable f => ToList (f a)

This instance makes ToList compatible and overlappable by Foldable.

Methods

toList :: f a -> [Element (f a)]

null :: f a -> Bool

TypeError Constraint (DisallowInstance "tuples") => ToList (a, b)

Methods

toList :: (a, b) -> [Element (a, b)]

null :: (a, b) -> Bool

ToList (f a) => ToList (WrappedList f a)

Methods

toList :: WrappedList f a -> [Element (WrappedList f a)]

null :: WrappedList f a -> Bool

class ToList t => Container t where

A class for ToLists that aren't trivial like Maybe (e.g. can hold more than one value)

Minimal complete definition

foldr, foldl, foldl', length, elem, maximum, minimum

Methods

foldMap :: Monoid m => (Element t -> m) -> t -> m

fold :: Monoid (Element t) => t -> Element t

foldr :: (Element t -> b -> b) -> b -> t -> b

foldr' :: (Element t -> b -> b) -> b -> t -> b

foldl :: (b -> Element t -> b) -> b -> t -> b

foldl' :: (b -> Element t -> b) -> b -> t -> b

foldr1 :: (Element t -> Element t -> Element t) -> t -> Element t

foldl1 :: (Element t -> Element t -> Element t) -> t -> Element t

length :: t -> Int

elem :: Eq (Element t) => Element t -> t -> Bool

notElem :: Eq (Element t) => Element t -> t -> Bool

maximum :: Ord (Element t) => t -> Element t

minimum :: Ord (Element t) => t -> Element t

all :: (Element t -> Bool) -> t -> Bool

any :: (Element t -> Bool) -> t -> Bool

and :: Element t ~ Bool => t -> Bool

or :: Element t ~ Bool => t -> Bool

find :: (Element t -> Bool) -> t -> Maybe (Element t)

head :: t -> Maybe (Element t)

Instances

Container ByteString

Methods

foldMap :: Monoid m => (Element ByteString -> m) -> ByteString -> m

fold :: ByteString -> Element ByteString

foldr :: (Element ByteString -> b -> b) -> b -> ByteString -> b

foldr' :: (Element ByteString -> b -> b) -> b -> ByteString -> b

foldl :: (b -> Element ByteString -> b) -> b -> ByteString -> b

foldl' :: (b -> Element ByteString -> b) -> b -> ByteString -> b

foldr1 :: (Element ByteString -> Element ByteString -> Element ByteString) -> ByteString -> Element ByteString

foldl1 :: (Element ByteString -> Element ByteString -> Element ByteString) -> ByteString -> Element ByteString

length :: ByteString -> Int

elem :: Element ByteString -> ByteString -> Bool

notElem :: Element ByteString -> ByteString -> Bool

maximum :: ByteString -> Element ByteString

minimum :: ByteString -> Element ByteString

all :: (Element ByteString -> Bool) -> ByteString -> Bool

any :: (Element ByteString -> Bool) -> ByteString -> Bool

and :: ByteString -> Bool

or :: ByteString -> Bool

find :: (Element ByteString -> Bool) -> ByteString -> Maybe (Element ByteString)

head :: ByteString -> Maybe (Element ByteString)

Container ByteString

Methods

foldMap :: Monoid m => (Element ByteString -> m) -> ByteString -> m

fold :: ByteString -> Element ByteString

foldr :: (Element ByteString -> b -> b) -> b -> ByteString -> b

foldr' :: (Element ByteString -> b -> b) -> b -> ByteString -> b

foldl :: (b -> Element ByteString -> b) -> b -> ByteString -> b

foldl' :: (b -> Element ByteString -> b) -> b -> ByteString -> b

foldr1 :: (Element ByteString -> Element ByteString -> Element ByteString) -> ByteString -> Element ByteString

foldl1 :: (Element ByteString -> Element ByteString -> Element ByteString) -> ByteString -> Element ByteString

length :: ByteString -> Int

elem :: Element ByteString -> ByteString -> Bool

notElem :: Element ByteString -> ByteString -> Bool

maximum :: ByteString -> Element ByteString

minimum :: ByteString -> Element ByteString

all :: (Element ByteString -> Bool) -> ByteString -> Bool

any :: (Element ByteString -> Bool) -> ByteString -> Bool

and :: ByteString -> Bool

or :: ByteString -> Bool

find :: (Element ByteString -> Bool) -> ByteString -> Maybe (Element ByteString)

head :: ByteString -> Maybe (Element ByteString)

Container IntSet

Methods

foldMap :: Monoid m => (Element IntSet -> m) -> IntSet -> m

fold :: IntSet -> Element IntSet

foldr :: (Element IntSet -> b -> b) -> b -> IntSet -> b

foldr' :: (Element IntSet -> b -> b) -> b -> IntSet -> b

foldl :: (b -> Element IntSet -> b) -> b -> IntSet -> b

foldl' :: (b -> Element IntSet -> b) -> b -> IntSet -> b

foldr1 :: (Element IntSet -> Element IntSet -> Element IntSet) -> IntSet -> Element IntSet

foldl1 :: (Element IntSet -> Element IntSet -> Element IntSet) -> IntSet -> Element IntSet

length :: IntSet -> Int

elem :: Element IntSet -> IntSet -> Bool

notElem :: Element IntSet -> IntSet -> Bool

maximum :: IntSet -> Element IntSet

minimum :: IntSet -> Element IntSet

all :: (Element IntSet -> Bool) -> IntSet -> Bool

any :: (Element IntSet -> Bool) -> IntSet -> Bool

and :: IntSet -> Bool

or :: IntSet -> Bool

find :: (Element IntSet -> Bool) -> IntSet -> Maybe (Element IntSet)

head :: IntSet -> Maybe (Element IntSet)

Container Text

Methods

foldMap :: Monoid m => (Element Text -> m) -> Text -> m

fold :: Text -> Element Text

foldr :: (Element Text -> b -> b) -> b -> Text -> b

foldr' :: (Element Text -> b -> b) -> b -> Text -> b

foldl :: (b -> Element Text -> b) -> b -> Text -> b

foldl' :: (b -> Element Text -> b) -> b -> Text -> b

foldr1 :: (Element Text -> Element Text -> Element Text) -> Text -> Element Text

foldl1 :: (Element Text -> Element Text -> Element Text) -> Text -> Element Text

length :: Text -> Int

elem :: Element Text -> Text -> Bool

notElem :: Element Text -> Text -> Bool

maximum :: Text -> Element Text

minimum :: Text -> Element Text

all :: (Element Text -> Bool) -> Text -> Bool

any :: (Element Text -> Bool) -> Text -> Bool

and :: Text -> Bool

or :: Text -> Bool

find :: (Element Text -> Bool) -> Text -> Maybe (Element Text)

head :: Text -> Maybe (Element Text)

Container Text

Methods

foldMap :: Monoid m => (Element Text -> m) -> Text -> m

fold :: Text -> Element Text

foldr :: (Element Text -> b -> b) -> b -> Text -> b

foldr' :: (Element Text -> b -> b) -> b -> Text -> b

foldl :: (b -> Element Text -> b) -> b -> Text -> b

foldl' :: (b -> Element Text -> b) -> b -> Text -> b

foldr1 :: (Element Text -> Element Text -> Element Text) -> Text -> Element Text

foldl1 :: (Element Text -> Element Text -> Element Text) -> Text -> Element Text

length :: Text -> Int

elem :: Element Text -> Text -> Bool

notElem :: Element Text -> Text -> Bool

maximum :: Text -> Element Text

minimum :: Text -> Element Text

all :: (Element Text -> Bool) -> Text -> Bool

any :: (Element Text -> Bool) -> Text -> Bool

and :: Text -> Bool

or :: Text -> Bool

find :: (Element Text -> Bool) -> Text -> Maybe (Element Text)

head :: Text -> Maybe (Element Text)

TypeError Constraint (DisallowInstance "Maybe") => Container (Maybe a)

Methods

foldMap :: Monoid m => (Element (Maybe a) -> m) -> Maybe a -> m

fold :: Maybe a -> Element (Maybe a)

foldr :: (Element (Maybe a) -> b -> b) -> b -> Maybe a -> b

foldr' :: (Element (Maybe a) -> b -> b) -> b -> Maybe a -> b

foldl :: (b -> Element (Maybe a) -> b) -> b -> Maybe a -> b

foldl' :: (b -> Element (Maybe a) -> b) -> b -> Maybe a -> b

foldr1 :: (Element (Maybe a) -> Element (Maybe a) -> Element (Maybe a)) -> Maybe a -> Element (Maybe a)

foldl1 :: (Element (Maybe a) -> Element (Maybe a) -> Element (Maybe a)) -> Maybe a -> Element (Maybe a)

length :: Maybe a -> Int

elem :: Element (Maybe a) -> Maybe a -> Bool

notElem :: Element (Maybe a) -> Maybe a -> Bool

maximum :: Maybe a -> Element (Maybe a)

minimum :: Maybe a -> Element (Maybe a)

all :: (Element (Maybe a) -> Bool) -> Maybe a -> Bool

any :: (Element (Maybe a) -> Bool) -> Maybe a -> Bool

and :: Maybe a -> Bool

or :: Maybe a -> Bool

find :: (Element (Maybe a) -> Bool) -> Maybe a -> Maybe (Element (Maybe a))

head :: Maybe a -> Maybe (Element (Maybe a))

Foldable f => Container (f a)

Methods

foldMap :: Monoid m => (Element (f a) -> m) -> f a -> m

fold :: f a -> Element (f a)

foldr :: (Element (f a) -> b -> b) -> b -> f a -> b

foldr' :: (Element (f a) -> b -> b) -> b -> f a -> b

foldl :: (b -> Element (f a) -> b) -> b -> f a -> b

foldl' :: (b -> Element (f a) -> b) -> b -> f a -> b

foldr1 :: (Element (f a) -> Element (f a) -> Element (f a)) -> f a -> Element (f a)

foldl1 :: (Element (f a) -> Element (f a) -> Element (f a)) -> f a -> Element (f a)

length :: f a -> Int

elem :: Element (f a) -> f a -> Bool

notElem :: Element (f a) -> f a -> Bool

maximum :: f a -> Element (f a)

minimum :: f a -> Element (f a)

all :: (Element (f a) -> Bool) -> f a -> Bool

any :: (Element (f a) -> Bool) -> f a -> Bool

and :: f a -> Bool

or :: f a -> Bool

find :: (Element (f a) -> Bool) -> f a -> Maybe (Element (f a))

head :: f a -> Maybe (Element (f a))

TypeError Constraint (DisallowInstance "Identity") => Container (Identity a)

Methods

foldMap :: Monoid m => (Element (Identity a) -> m) -> Identity a -> m

fold :: Identity a -> Element (Identity a)

foldr :: (Element (Identity a) -> b -> b) -> b -> Identity a -> b

foldr' :: (Element (Identity a) -> b -> b) -> b -> Identity a -> b

foldl :: (b -> Element (Identity a) -> b) -> b -> Identity a -> b

foldl' :: (b -> Element (Identity a) -> b) -> b -> Identity a -> b

foldr1 :: (Element (Identity a) -> Element (Identity a) -> Element (Identity a)) -> Identity a -> Element (Identity a)

foldl1 :: (Element (Identity a) -> Element (Identity a) -> Element (Identity a)) -> Identity a -> Element (Identity a)

length :: Identity a -> Int

elem :: Element (Identity a) -> Identity a -> Bool

notElem :: Element (Identity a) -> Identity a -> Bool

maximum :: Identity a -> Element (Identity a)

minimum :: Identity a -> Element (Identity a)

all :: (Element (Identity a) -> Bool) -> Identity a -> Bool

any :: (Element (Identity a) -> Bool) -> Identity a -> Bool

and :: Identity a -> Bool

or :: Identity a -> Bool

find :: (Element (Identity a) -> Bool) -> Identity a -> Maybe (Element (Identity a))

head :: Identity a -> Maybe (Element (Identity a))

TypeError Constraint (DisallowInstance "Either") => Container (Either a b)

Methods

foldMap :: Monoid m => (Element (Either a b) -> m) -> Either a b -> m

fold :: Either a b -> Element (Either a b)

foldr :: (Element (Either a b) -> b -> b) -> b -> Either a b -> b

foldr' :: (Element (Either a b) -> b -> b) -> b -> Either a b -> b

foldl :: (b -> Element (Either a b) -> b) -> b -> Either a b -> b

foldl' :: (b -> Element (Either a b) -> b) -> b -> Either a b -> b

foldr1 :: (Element (Either a b) -> Element (Either a b) -> Element (Either a b)) -> Either a b -> Element (Either a b)

foldl1 :: (Element (Either a b) -> Element (Either a b) -> Element (Either a b)) -> Either a b -> Element (Either a b)

length :: Either a b -> Int

elem :: Element (Either a b) -> Either a b -> Bool

notElem :: Element (Either a b) -> Either a b -> Bool

maximum :: Either a b -> Element (Either a b)

minimum :: Either a b -> Element (Either a b)

all :: (Element (Either a b) -> Bool) -> Either a b -> Bool

any :: (Element (Either a b) -> Bool) -> Either a b -> Bool

and :: Either a b -> Bool

or :: Either a b -> Bool

find :: (Element (Either a b) -> Bool) -> Either a b -> Maybe (Element (Either a b))

head :: Either a b -> Maybe (Element (Either a b))

TypeError Constraint (DisallowInstance "tuples") => Container (a, b)

Methods

foldMap :: Monoid m => (Element (a, b) -> m) -> (a, b) -> m

fold :: (a, b) -> Element (a, b)

foldr :: (Element (a, b) -> b -> b) -> b -> (a, b) -> b

foldr' :: (Element (a, b) -> b -> b) -> b -> (a, b) -> b

foldl :: (b -> Element (a, b) -> b) -> b -> (a, b) -> b

foldl' :: (b -> Element (a, b) -> b) -> b -> (a, b) -> b

foldr1 :: (Element (a, b) -> Element (a, b) -> Element (a, b)) -> (a, b) -> Element (a, b)

foldl1 :: (Element (a, b) -> Element (a, b) -> Element (a, b)) -> (a, b) -> Element (a, b)

length :: (a, b) -> Int

elem :: Element (a, b) -> (a, b) -> Bool

notElem :: Element (a, b) -> (a, b) -> Bool

maximum :: (a, b) -> Element (a, b)

minimum :: (a, b) -> Element (a, b)

all :: (Element (a, b) -> Bool) -> (a, b) -> Bool

any :: (Element (a, b) -> Bool) -> (a, b) -> Bool

and :: (a, b) -> Bool

or :: (a, b) -> Bool

find :: (Element (a, b) -> Bool) -> (a, b) -> Maybe (Element (a, b))

head :: (a, b) -> Maybe (Element (a, b))

ToList (f a) => Container (WrappedList f a)

Methods

foldMap :: Monoid m => (Element (WrappedList f a) -> m) -> WrappedList f a -> m

fold :: WrappedList f a -> Element (WrappedList f a)

foldr :: (Element (WrappedList f a) -> b -> b) -> b -> WrappedList f a -> b

foldr' :: (Element (WrappedList f a) -> b -> b) -> b -> WrappedList f a -> b

foldl :: (b -> Element (WrappedList f a) -> b) -> b -> WrappedList f a -> b

foldl' :: (b -> Element (WrappedList f a) -> b) -> b -> WrappedList f a -> b

foldr1 :: (Element (WrappedList f a) -> Element (WrappedList f a) -> Element (WrappedList f a)) -> WrappedList f a -> Element (WrappedList f a)

foldl1 :: (Element (WrappedList f a) -> Element (WrappedList f a) -> Element (WrappedList f a)) -> WrappedList f a -> Element (WrappedList f a)

length :: WrappedList f a -> Int

elem :: Element (WrappedList f a) -> WrappedList f a -> Bool

notElem :: Element (WrappedList f a) -> WrappedList f a -> Bool

maximum :: WrappedList f a -> Element (WrappedList f a)

minimum :: WrappedList f a -> Element (WrappedList f a)

all :: (Element (WrappedList f a) -> Bool) -> WrappedList f a -> Bool

any :: (Element (WrappedList f a) -> Bool) -> WrappedList f a -> Bool

and :: WrappedList f a -> Bool

or :: WrappedList f a -> Bool

find :: (Element (WrappedList f a) -> Bool) -> WrappedList f a -> Maybe (Element (WrappedList f a))

head :: WrappedList f a -> Maybe (Element (WrappedList f a))

type NontrivialContainer t = Container t

To save backwards compatibility with previous naming.

newtype WrappedList f a

This can be useful if you want to use Container methods for your data type but you don't want to implement all methods of this type class for that.

Constructors

WrappedList (f a)

Instances

ToList (f a) => Container (WrappedList f a)

Methods

foldMap :: Monoid m => (Element (WrappedList f a) -> m) -> WrappedList f a -> m

fold :: WrappedList f a -> Element (WrappedList f a)

foldr :: (Element (WrappedList f a) -> b -> b) -> b -> WrappedList f a -> b

foldr' :: (Element (WrappedList f a) -> b -> b) -> b -> WrappedList f a -> b

foldl :: (b -> Element (WrappedList f a) -> b) -> b -> WrappedList f a -> b

foldl' :: (b -> Element (WrappedList f a) -> b) -> b -> WrappedList f a -> b

foldr1 :: (Element (WrappedList f a) -> Element (WrappedList f a) -> Element (WrappedList f a)) -> WrappedList f a -> Element (WrappedList f a)

foldl1 :: (Element (WrappedList f a) -> Element (WrappedList f a) -> Element (WrappedList f a)) -> WrappedList f a -> Element (WrappedList f a)

length :: WrappedList f a -> Int

elem :: Element (WrappedList f a) -> WrappedList f a -> Bool

notElem :: Element (WrappedList f a) -> WrappedList f a -> Bool

maximum :: WrappedList f a -> Element (WrappedList f a)

minimum :: WrappedList f a -> Element (WrappedList f a)

all :: (Element (WrappedList f a) -> Bool) -> WrappedList f a -> Bool

any :: (Element (WrappedList f a) -> Bool) -> WrappedList f a -> Bool

and :: WrappedList f a -> Bool

or :: WrappedList f a -> Bool

find :: (Element (WrappedList f a) -> Bool) -> WrappedList f a -> Maybe (Element (WrappedList f a))

head :: WrappedList f a -> Maybe (Element (WrappedList f a))

ToList (f a) => ToList (WrappedList f a)

Methods

toList :: WrappedList f a -> [Element (WrappedList f a)]

null :: WrappedList f a -> Bool

type Element (WrappedList f a)

type Element (WrappedList f a) = a

sum :: (Container t, Num (Element t)) => t -> Element t

Stricter version of sum.

>>> sum [1..10]
55
>>> sum (Just 3)
<interactive>:43:1: error:
    • Do not use 'Foldable' methods on Maybe
    • In the expression: sum (Just 3)
      In an equation for ‘it’: it = sum (Just 3)

product :: (Container t, Num (Element t)) => t -> Element t

Stricter version of product.

>>> product [1..10]
3628800
>>> product (Right 3)
<interactive>:45:1: error:
    • Do not use 'Foldable' methods on Either
    • In the expression: product (Right 3)
      In an equation for ‘it’: it = product (Right 3)

mapM_ :: (Container t, Monad m) => (Element t -> m b) -> t -> m ()

Constrained to Container version of mapM_.

forM_ :: (Container t, Monad m) => t -> (Element t -> m b) -> m ()

Constrained to Container version of forM_.

traverse_ :: (Container t, Applicative f) => (Element t -> f b) -> t -> f ()

Constrained to Container version of traverse_.

for_ :: (Container t, Applicative f) => t -> (Element t -> f b) -> f ()

Constrained to Container version of for_.

sequenceA_ :: (Container t, Applicative f, Element t ~ f a) => t -> f ()

Constrained to Container version of sequenceA_.

sequence_ :: (Container t, Monad m, Element t ~ m a) => t -> m ()

Constrained to Container version of sequence_.

asum :: (Container t, Alternative f, Element t ~ f a) => t -> f a

Constrained to Container version of asum.

Others

class One x where

Type class for types that can be created from one element. singleton is lone name for this function. Also constructions of different type differ: :[] for lists, two arguments for Maps. Also some data types are monomorphic.

>>> one True :: [Bool]
[True]
>>> one 'a' :: Text
"a"
>>> one (3, "hello") :: HashMap Int String
fromList [(3,"hello")]

Minimal complete definition

one

Associated Types

type OneItem x

Methods

one :: OneItem x -> x

Create a list, map, Text, etc from a single element.

Instances

One ByteString

Associated Types

type OneItem ByteString :: *

Methods

one :: OneItem ByteString -> ByteString

One ByteString

Associated Types

type OneItem ByteString :: *

Methods

one :: OneItem ByteString -> ByteString

One IntSet

Associated Types

type OneItem IntSet :: *

Methods

one :: OneItem IntSet -> IntSet

One Text

Associated Types

type OneItem Text :: *

Methods

one :: OneItem Text -> Text

One Text

Associated Types

type OneItem Text :: *

Methods

one :: OneItem Text -> Text

One [a]

Associated Types

type OneItem [a] :: *

Methods

one :: OneItem [a] -> [a]

One (NonEmpty a)

Associated Types

type OneItem (NonEmpty a) :: *

Methods

one :: OneItem (NonEmpty a) -> NonEmpty a

One (IntMap v)

Associated Types

type OneItem (IntMap v) :: *

Methods

one :: OneItem (IntMap v) -> IntMap v

One (Seq a)

Associated Types

type OneItem (Seq a) :: *

Methods

one :: OneItem (Seq a) -> Seq a

One (Set v)

Associated Types

type OneItem (Set v) :: *

Methods

one :: OneItem (Set v) -> Set v

Hashable v => One (HashSet v)

Associated Types

type OneItem (HashSet v) :: *

Methods

one :: OneItem (HashSet v) -> HashSet v

One (Vector a)

Associated Types

type OneItem (Vector a) :: *

Methods

one :: OneItem (Vector a) -> Vector a

Storable a => One (Vector a)

Associated Types

type OneItem (Vector a) :: *

Methods

one :: OneItem (Vector a) -> Vector a

Unbox a => One (Vector a)

Associated Types

type OneItem (Vector a) :: *

Methods

one :: OneItem (Vector a) -> Vector a

Prim a => One (Vector a)

Associated Types

type OneItem (Vector a) :: *

Methods

one :: OneItem (Vector a) -> Vector a

One (Map k v)

Associated Types

type OneItem (Map k v) :: *

Methods

one :: OneItem (Map k v) -> Map k v

Hashable k => One (HashMap k v)

Associated Types

type OneItem (HashMap k v) :: *

Methods

one :: OneItem (HashMap k v) -> HashMap k v