Modulefs-sim-0.5.0.1Haskell2010

System.FS.Sim.Stream

Finite and infinite streams of Maybe as.

2 types
18 values

Packagefs-sim-0.5.0.1
Exports20
LanguageHaskell2010
LicenceApache-2.0
SourceStream.hs

Streams

2 declarations

datadata Stream a

A stream of Maybe as that can be infinite.

Constructors

UnsafeStream
UNSAFE: when constructing, modifying, or accessing the internals of a Stream, it is the responsibility of the user to preserve the following invariant:
INVARIANT: if the stream is marked as Infinite, then the internal list should be infinite. If the stream is marked as Finite, then the internal list should finite.
- If the internal list is infinite but marked as Finite, then shrink or show on the corresponding stream will diverge.
- If the internal list is finite but marked as Infinite, then shrink on the corresponding stream will degrade to an infinite list of empty streams.
- unsafeStreamInternalInfo :: InternalInfo
  UNSAFE: see UnsafeStream for more information.
  Info about the finiteness of the stream. It is used for shrinking and the Show instance.
- unsafeStreamList :: [Maybe a]
  UNSAFE: see UnsafeStream for more information.
  The internal list underlying the stream.

Instances2Functor, Show

Functor StreamDefined in fs-sim-0.5.0.1 · System.FS.Sim.Stream
Show a => Show (Stream a)Defined in fs-sim-0.5.0.1 · System.FS.Sim.Stream
Fully shows a Stream if it is finite, or prints a placeholder string if it is infinite.

datadata InternalInfo

Tag for Streams that describes whether it is finite or infinite.

Useful for the Show instance of Stream: when a Stream is finite, we can safely print the full stream.

Infinite Finite

Running

3 declarations

valuerunStream :: Stream a -> (Maybe a, Stream a)

O(1) : advance the Stream. Return the Maybe a and the remaining Stream.

Returns Nothing by default if the Stream is empty.

valuerunStreamN :: Int -> Stream a -> ([Maybe a], Stream a)

O(n) : like runStream, but advancing the stream n times.

If n<=0, then the stream is advanced 0 times.

valuerunStreamIndefinitely :: Stream a -> [Maybe a]

O(\infty) : like runStream, but advancing the stream indefinitely.

For infinite streams, this produces an infinite list. For finite streams, this produces a finite list.

Construction

5 declarations

valuealways :: a -> Stream a

Make a Stream that always generates the given a.

valueempty :: Stream a

Make an empty Stream.

valuerepeating :: [Maybe a] -> Stream a

Make a Stream that infinitely repeats the given list.

valueunsafeMkInfinite :: [Maybe a] -> Stream a

UNSAFE: Make a Stream that is marked as infinite. It is the user's responsibility to only pass in infinite lists. See UnsafeStream for more information.

valueunsafeMkFinite :: [Maybe a] -> Stream a

UNSAFE: Make a Stream that is marked as finite. It is the user's responsibility to only pass in finite lists. See UnsafeStream for more information.

Modify

1 declaration

valuefilter :: (Maybe a -> Bool) -> Stream a -> Stream a

Filter a Stream, preserving finiteness.

Query

3 declarations

valuenull :: Stream a -> Bool

Check that the stream is empty.

In general, a stream is only empty if the stream is equivalent to empty.

A finite/infinite stream consisting of only Nothings is not considered to be empty. In particular, null (always Nothing) /= True.

valueisFinite :: Stream a -> Bool

Check that the stream is finite

valueisInfinite :: Stream a -> Bool

Check that the stream is infinite

Generation and shrinking

6 declarations

valuegenFinite :: Gen (Maybe a) -> Gen (Stream a)

Generate a sized, finite Stream.

valuegenFiniteN

:: Int
Requested size of finite stream.
-> Gen (Maybe a)
-> Gen (Stream a)

Generate a finite Stream of length n.

valuegenInfinite :: Gen (Maybe a) -> Gen (Stream a)

Generate an infinite Stream.

valuegenMaybe

:: Int
Likelihood of Nothing
-> Int
Likelihood of Just a
-> Gen a
-> Gen (Maybe a)

Make a Maybe a generator based on an a generator.

Each element has a chance of being either Nothing or an element generated with the given a generator (wrapped in a Just). These likelihoods are passed to frequency.

valueshrinkStream :: Stream a -> [Stream a]

Shrink a stream like it is an InfiniteList.

Infinite streams are shrunk differently than lists that are finite, which is to ensure that we shrink infinite lists towards finite lists.

Infinite streams are shrunk by taking finite prefixes of the argument stream. Note that there are an infinite number of finite prefixes, so even though the *shrink list* is infinite, the individual *list elements* are finite.
Finite streams are shrunk like lists are shrunk normally, preserving finiteness.

valueliftShrinkStream :: (Maybe a -> [Maybe a]) -> Stream a -> [Stream a]

Like shrinkStream, but with a custom shrinker for elements of the stream.