DA.Foldable
DA.Foldable
Class of data structures that can be folded to a summary value.
It’s a good idea to import this module qualified to avoid clashes with
functions defined in Prelude. Ie.:
import DA.Foldable qualified as F
Typeclasses
class Foldable t where
Class of data structures that can be folded to a summary value.
fold: Monoid m => t m -> m
Combine the elements of a structure using a monoid.
foldMap: Monoid m => (a -> m) -> t a -> m
Combine the elements of a structure using a monoid.
foldr: (a -> b -> b) -> b -> t a -> b
Right-associative fold of a structure.
foldl: (b -> a -> b) -> b -> t a -> b
Left-associative fold of a structure.
foldr1: (a -> a -> a) -> t a -> a
A variant of foldr that has no base case, and thus should only be applied to non-empty structures.
foldl1: (a -> a -> a) -> t a -> a
A variant of foldl that has no base case, and thus should only be applied to non-empty structures.
toList: t a -> [a]
List of elements of a structure, from left to right.
null: t a -> Bool
Test whether the structure is empty. The default implementation is optimized for structures that are similar to cons-lists, because there is no general way to do better.
length: t a -> Int
Returns the size/length of a finite structure as an
elemInt. The default implementation is optimized for structures that are similar to cons-lists, because there is no general way to do better.Does the element occur in the structure?
sum: Additive a => t a -> a
The sum function computes the sum of the numbers of a structure.
product: Multiplicative a => t a -> a
The product function computes the product of the numbers of a structure.
minimum: Ord a => t a -> a
The least element of a non-empty structure.
maximum: Ord a => t a -> a
The largest element of a non-empty structure.
instance Ord k => Foldable (Map k)
instance Foldable (Validation err)
instance Foldable a
Functions
mapA_: (Foldable t, Applicative f) => (a -> f b) -> t a -> f ()
Map each element of a structure to an action, evaluate these actions from left to right, and ignore the results. For a version that doesn’t ignore the results see ‘DA.Traversable.mapA’.
forA_: (Foldable t, Applicative f) => t a -> (a -> f b) -> f ()
‘for_’ is ‘mapA_’ with its arguments flipped. For a version that doesn’t ignore the results see ‘DA.Traversable.forA’.
forM_: (Foldable t, Applicative f) => t a -> (a -> f b) -> f ()
Warning
DEPRECATED:
: (Foldable t, Action m) => t (m a) -> m ()
Evaluate each action in the structure from left to right, and ignore the results. For a version that doesn’t ignore the results see ‘DA.Traversable.sequence’.
concat: Foldable t => t [a] -> [a]
The concatenation of all the elements of a container of lists.
and: Foldable t => t Bool -> Bool
and returns the conjunction of a container of Bools. For the result to be True, the container must be finite; False, however, results from a False value finitely far from the left end.
: Foldable t => t Bool -> Bool
or returns the disjunction of a container of Bools. For the result to be False, the container must be finite; True, however, results from a True value finitely far from the left end.
: Foldable t => (a -> Bool) -> t a -> Bool
Determines whether any element of the structure satisfies the predicate.
all: Foldable t => (a -> Bool) -> t a -> Bool
Determines whether all elements of the structure satisfy the predicate.
