An Unfold m a b is a generator of a stream of values of type b from a seed of type a in Monad m.

Since: 0.7.0

Make an unfold from step and inject functions.

Pre-release

Make an unfold from a step function.

See also: unfoldrM

Pre-release

Build a stream by unfolding a monadic step function starting from a seed. The step function returns the next element in the stream and the next seed value. When it is done it returns Nothing and the stream ends.

Since: 0.8.0

Like unfoldrM but uses a pure step function.

>>> :{
 f [] = Nothing
 f (x:xs) = Just (x, xs)
:}

>>> Unfold.fold Fold.toList (Unfold.unfoldr f) [1,2,3]
[1,2,3]

Since: 0.8.0

Lift a monadic function into an unfold. The unfold generates a singleton stream.

Since: 0.8.0

Lift a pure function into an unfold. The unfold generates a singleton stream.

function f = functionM $ return . f

Since: 0.8.0

Identity unfold. The unfold generates a singleton stream having the input as the only element.

identity = function Prelude.id

Pre-release

The unfold discards its input and generates a function stream using the supplied monadic action.

Pre-release

Discards the unfold input and always returns the argument of fromPure.

fromPure = fromEffect . pure

Pre-release

Map a function on the input argument of the Unfold.

>>> u = Unfold.lmap (fmap (+1)) Unfold.fromList
>>> Unfold.fold Fold.toList u [1..5]
[2,3,4,5,6]

lmap f = Unfold.many (Unfold.function f)

Since: 0.8.0

Map an action on the input argument of the Unfold.

lmapM f = Unfold.many (Unfold.functionM f)

Since: 0.8.0

Map a function on the output of the unfold (the type b).

Pre-release

Supply the seed to an unfold closing the input end of the unfold.

supply a = Unfold.lmap (Prelude.const a)

Pre-release

Supply the first component of the tuple to an unfold that accepts a tuple as a seed resulting in a fold that accepts the second component of the tuple as a seed.

supplyFirst a = Unfold.lmap (a, )

Pre-release

Supply the second component of the tuple to an unfold that accepts a tuple as a seed resulting in a fold that accepts the first component of the tuple as a seed.

supplySecond b = Unfold.lmap (, b)

Pre-release

Same as takeWhile but with a monadic predicate.

Since: 0.8.0

End the stream generated by the Unfold as soon as the predicate fails on an element.

Since: 0.8.0

Apply the second unfold to each output element of the first unfold and flatten the output in a single stream.

Since: 0.8.0

unfoldManyInterleave for documentation and notes.

This is almost identical to unfoldManyInterleave in StreamD module.

The many combinator is in fact manyAppend to be more explicit in naming.

Internal

Outer product discarding the first element.

Unimplemented

Outer product discarding the second element.

Unimplemented

Create a cross product (vector product or cartesian product) of the output streams of two unfolds using a monadic combining function.

Pre-release

Like crossWithM but uses a pure combining function.

crossWith f = crossWithM (\b c -> return $ f b c)

>>> u1 = Unfold.lmap fst Unfold.fromList
>>> u2 = Unfold.lmap snd Unfold.fromList
>>> u = Unfold.crossWith (,) u1 u2
>>> Unfold.fold Fold.toList u ([1,2,3], [4,5,6])
[(1,4),(1,5),(1,6),(2,4),(2,5),(2,6),(3,4),(3,5),(3,6)]

Since: 0.8.0

See crossWith.

cross = crossWith (,)

To cross the streams from a tuple we can write:

crossProduct :: Monad m => Unfold m a b -> Unfold m c d -> Unfold m (a, c) (b, d)
crossProduct u1 u2 = cross (lmap fst u1) (lmap snd u2)

Pre-release

Map an unfold generating action to each element of an unfold and flatten the results into a single stream.

Distribute the input to two unfolds and then zip the outputs to a single stream using a monadic zip function.

Stops as soon as any of the unfolds stops.

Pre-release

Like zipWithM but with a pure zip function.

>>> square = fmap (\x -> x * x) Unfold.fromList
>>> cube = fmap (\x -> x * x * x) Unfold.fromList
>>> u = Unfold.zipWith (,) square cube
>>> Unfold.fold Fold.toList u [1..5]
[(1,1),(4,8),(9,27),(16,64),(25,125)]

zipWith f = zipWithM (\a b -> return $ f a b)

Since: 0.8.0