Pinch.Internal.FoldList

Implements a representation of a list as a fold over it.

Documentation

data FoldList a

FoldList represents a list as a foldl' traversal over it.

This allows us to avoid allocating new collections for an intermediate representation of various data types that users provide.

Instances

Functor FoldList

Defined in Pinch.Internal.FoldList

Methods

fmap :: (a -> b) -> FoldList a -> FoldList b

(<$) :: a -> FoldList b -> FoldList a

Foldable FoldList

Defined in Pinch.Internal.FoldList

Methods

fold :: Monoid m => FoldList m -> m

foldMap :: Monoid m => (a -> m) -> FoldList a -> m

foldr :: (a -> b -> b) -> b -> FoldList a -> b

foldr' :: (a -> b -> b) -> b -> FoldList a -> b

foldl :: (b -> a -> b) -> b -> FoldList a -> b

foldl' :: (b -> a -> b) -> b -> FoldList a -> b

foldr1 :: (a -> a -> a) -> FoldList a -> a

foldl1 :: (a -> a -> a) -> FoldList a -> a

toList :: FoldList a -> [a]

null :: FoldList a -> Bool

length :: FoldList a -> Int

elem :: Eq a => a -> FoldList a -> Bool

maximum :: Ord a => FoldList a -> a

minimum :: Ord a => FoldList a -> a

sum :: Num a => FoldList a -> a

product :: Num a => FoldList a -> a

Traversable FoldList

Defined in Pinch.Internal.FoldList

Methods

traverse :: Applicative f => (a -> f b) -> FoldList a -> f (FoldList b)

sequenceA :: Applicative f => FoldList (f a) -> f (FoldList a)

mapM :: Monad m => (a -> m b) -> FoldList a -> m (FoldList b)

sequence :: Monad m => FoldList (m a) -> m (FoldList a)

Eq a => Eq (FoldList a)

Defined in Pinch.Internal.FoldList

Methods

(==) :: FoldList a -> FoldList a -> Bool

(/=) :: FoldList a -> FoldList a -> Bool

Show a => Show (FoldList a)

Defined in Pinch.Internal.FoldList

Methods

showsPrec :: Int -> FoldList a -> ShowS

show :: FoldList a -> String

showList :: [FoldList a] -> ShowS

Semigroup (FoldList a)

Defined in Pinch.Internal.FoldList

Methods

(<>) :: FoldList a -> FoldList a -> FoldList a

sconcat :: NonEmpty (FoldList a) -> FoldList a

stimes :: Integral b => b -> FoldList a -> FoldList a

Monoid (FoldList a)

Defined in Pinch.Internal.FoldList

Methods

mempty :: FoldList a

mappend :: FoldList a -> FoldList a -> FoldList a

mconcat :: [FoldList a] -> FoldList a

NFData a => NFData (FoldList a)

Defined in Pinch.Internal.FoldList

Methods

rnf :: FoldList a -> ()

Hashable a => Hashable (FoldList a)

Defined in Pinch.Internal.FoldList

Methods

hashWithSalt :: Int -> FoldList a -> Int

hash :: FoldList a -> Int

map :: (a -> b) -> FoldList a -> FoldList b

Applies the given function to all elements in the FoldList.

Note that the function is applied lazily when the results are requested. If the results of the same FoldList are requested multiple times, the function will be called multiple times on the same elements.

replicate :: Int -> a -> FoldList a

Returns a FoldList with the given item repeated n times.

replicateM :: Monad m => Int -> m a -> m (FoldList a)

Executes the given monadic action the given number of times and returns a FoldList of the results.

foldl' :: Foldable t => (b -> a -> b) -> b -> t a -> b

Left-associative fold of a structure but with strict application of the operator.

This ensures that each step of the fold is forced to weak head normal form before being applied, avoiding the collection of thunks that would otherwise occur. This is often what you want to strictly reduce a finite list to a single, monolithic result (e.g. length).

For a general Foldable structure this should be semantically identical to,

foldl f z = foldl' f z . toList

foldr :: Foldable t => (a -> b -> b) -> b -> t a -> b

Right-associative fold of a structure.

In the case of lists, foldr, when applied to a binary operator, a starting value (typically the right-identity of the operator), and a list, reduces the list using the binary operator, from right to left:

foldr f z [x1, x2, ..., xn] == x1 `f` (x2 `f` ... (xn `f` z)...)

Note that, since the head of the resulting expression is produced by an application of the operator to the first element of the list, foldr can produce a terminating expression from an infinite list.

For a general Foldable structure this should be semantically identical to,

foldr f z = foldr f z . toList

toList :: Foldable t => t a -> [a]

List of elements of a structure, from left to right.

fromFoldable :: Foldable f => f a -> FoldList a

Builds a FoldList from a Foldable.

fromMap

Arguments

:: (forall r. (r -> k -> v -> r) -> r -> m k v -> r)

foldlWithKey provided by the map implementation.

-> m k v

-> FoldList (k, v)

Builds a FoldList over pairs of items of a map.

mapM :: (Traversable t, Monad m) => (a -> m b) -> t a -> m (t b)

Map each element of a structure to a monadic action, evaluate these actions from left to right, and collect the results. For a version that ignores the results see mapM_.

sequence :: (Traversable t, Monad m) => t (m a) -> m (t a)

Evaluate each monadic action in the structure from left to right, and collect the results. For a version that ignores the results see sequence_.