Fold.Pure.Examples

General

magma :: (a -> a -> a) -> Fold a (Maybe a)

Start with the first input, append each new input on the right with the given function

semigroup :: Semigroup a => Fold a (Maybe a)

Append each new input on the right with (<>)

monoid :: Monoid a => Fold a a

Start with mempty, append each input on the right with (<>)

Endpoints

first :: Fold a (Maybe a)

The first input

last :: Fold a (Maybe a)

The last input

Extrema

maximum :: Ord a => Fold a (Maybe a)

The greatest input

minimum :: Ord a => Fold a (Maybe a)

The least input

maximumBy :: (a -> a -> Ordering) -> Fold a (Maybe a)

The greatest input with respect to the given comparison function

minimumBy :: (a -> a -> Ordering) -> Fold a (Maybe a)

The least input with respect to the given comparison function

Length

null :: Fold a Bool

True if the input contains no inputs

length :: Fold a Natural

The number of inputs

Boolean

and :: Fold Bool Bool

True if all inputs are True

or :: Fold Bool Bool

True if any input is True

all :: (a -> Bool) -> Fold a Bool

True if all inputs satisfy the predicate

any :: (a -> Bool) -> Fold a Bool

True if any input satisfies the predicate

Numeric

sum :: Num a => Fold a a

Adds the inputs

product :: Num a => Fold a a

Multiplies the inputs

mean :: Fractional a => Fold a a

Numerically stable arithmetic mean of the inputs

variance :: Fractional a => Fold a a

Numerically stable (population) variance over the inputs

standardDeviation :: Floating a => Fold a a

Numerically stable (population) standard deviation over the inputs

Search

element :: Eq a => a -> Fold a Bool

True if any input is equal to the given value

notElement :: Eq a => a -> Fold a Bool

False if any input is equal to the given value

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

The first input that satisfies the predicate, if any

lookup :: Eq a => a -> Fold (a, b) (Maybe b)

The b from the first tuple where a equals the given value, if any

Index

index :: Natural -> Fold a (Maybe a)

The nth input, where n=0 is the first input, if the index is in bounds

findIndex :: (a -> Bool) -> Fold a (Maybe Natural)

The index of the first input that satisfies the predicate, if any

elementIndex :: Eq a => a -> Fold a (Maybe Natural)

The index of the first input that matches the given value, if any

List

list :: Fold a [a]

All the inputs

reverseList :: Fold a [a]

All the inputs in reverse order