Safe Haskell	Safe-Inferred
Language	Haskell2010

System.FS.Sim.Stream

Contents

Streams
Running
Construction
Query
Generation and shrinking

Description

Possibly infinite streams of Maybe as.

Synopsis

data Stream a
runStream ∷ Stream a → (Maybe a, Stream a)
always ∷ a → Stream a
empty ∷ Stream a
mkInfinite ∷ [Maybe a] → Stream a
repeating ∷ [Maybe a] → Stream a
unsafeMkFinite ∷ [Maybe a] → Stream a
null ∷ Stream a → Bool
genFinite ∷ Int → Gen (Maybe a) → Gen (Stream a)
genInfinite ∷ Gen (Maybe a) → Gen (Stream a)
genMaybe ∷ Int → Int → Gen a → Gen (Maybe a)
genMaybe' ∷ Int → Gen a → Gen (Maybe a)
shrinkStream ∷ Stream a → [Stream a]

Streams

data Stream a Source #

A Stream is a stream of Maybe as, which is possibly infinite or definitely finite.

Finiteness is tracked internally and used for shrinking and the Show instance.

Instances

Instances details

Functor Stream Source #
Instance details Defined in System.FS.Sim.Stream Methods fmap ∷ (a → b) → Stream a → Stream b # (<$) ∷ a → Stream b → Stream a #
Show a ⇒ Show (Stream a) Source #	Fully shows a `Stream` if it is definitely finite, or prints a placeholder string if it is possibly infinite.
Instance details Defined in System.FS.Sim.Stream Methods showsPrec ∷ Int → Stream a → ShowS # show ∷ Stream a → String # showList ∷ [Stream a] → ShowS #

Running

runStream ∷ Stream a → (Maybe a, Stream a) Source #

Advance the Stream. Return the Maybe a and the remaining Stream.

Returns Nothing by default if the Stream is empty.

Construction

always ∷ a → Stream a Source #

Make a Stream that always generates the given a.

empty ∷ Stream a Source #

Make an empty Stream.

mkInfinite ∷ [Maybe a] → Stream a Source #

Make a Stream that is marked as possibly infinite.

repeating ∷ [Maybe a] → Stream a Source #

Make a Stream that infinitely repeats the given list.

unsafeMkFinite ∷ [Maybe a] → Stream a Source #

UNSAFE: Make a Stream that is marked as definitely finite.

This is unsafe since a user can pass in any list, and evaluating shrink or show on the resulting Stream will diverge. It is the user's responsibility to only pass in a finite list.

Query

null ∷ Stream a → Bool Source #

Return True if the stream is empty.

A stream consisting of only Nothings (even if it is only one) is not considered to be empty.

Generation and shrinking

genFinite Source #

Arguments

∷ Int	Requested size of finite stream. Tip: use `genMaybe`.
→ Gen (Maybe a)
→ Gen (Stream a)

Generate a finite Stream of length n.

genInfinite Source #

Arguments

∷ Gen (Maybe a)	Tip: use `genMaybe`.
→ Gen (Stream a)

Generate an infinite Stream.

genMaybe Source #

Arguments

∷ 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).

The first argument is the likelihood (as used by frequency) of a Just where Nothing has likelihood 2.

genMaybe' Source #

Arguments

∷ Int	Likelihood of `Just a`
→ Gen a
→ Gen (Maybe a)

Like genMaybe, but with the likelihood of Nothing fixed to 2. frequency

shrinkStream ∷ Stream a → [Stream a] Source #

Shrink a stream like it is an InfiniteList.

Possibly infinite streams are shrunk differently than lists that are definitely finite, which is to ensure that shrinking terminates. * Possibly infinite streams are shrunk by taking finite prefixes of the argument stream. As such, shrinking a possibly infinite stream creates definitely finite streams. * Definitely finite streams are shrunk like lists are shrunk normally, preserving that the created streams are still definitely finite.