Test.QuickCheck.Gen

newtype Gen a

The random generator monad

Gen is a state monad which encodes a linear congruential generator.

Instances

• Functor Gen
• Apply Gen
• Applicative Gen
• Bind Gen
• Monad Gen
• Alt Gen
• MonadRec Gen
• Lazy (Gen a)
• MonadGen Gen

unGen :: forall a. Gen a -> State GenState a

Exposes the underlying State implementation.

type GenState = { newSeed :: Seed, size :: Size }

The state of the random generator monad

type Size = Int

Tests are parameterized by the Size of the randomly-generated data, the meaning of which depends on the particular generator used.

repeatable :: forall a b. (a -> Gen b) -> Gen (a -> b)

Create a random generator for a function type.

stateful :: forall a. (GenState -> Gen a) -> Gen a

Create a random generator which uses the generator state explicitly.

variant :: forall a. Seed -> Gen a -> Gen a

Modify a random generator by setting a new random seed.

suchThat :: forall a. Gen a -> (a -> Boolean) -> Gen a

Ensure that a generator only produces values that match a predicate. If the predicate always returns false the generator will loop forever.

sized :: forall a. (Size -> Gen a) -> Gen a

Create a random generator which depends on the size parameter.

resize :: forall a. Size -> Gen a -> Gen a

Modify a random generator by setting a new size parameter.

choose :: Number -> Number -> Gen Number

Create a random generator which samples a range of Numbers i with uniform probability.

chooseInt :: Int -> Int -> Gen Int

Create a random generator which chooses uniformly distributed integers from the closed interval [a, b]. Note that very large intervals will cause a loss of uniformity.

oneOf :: forall a. NonEmptyArray (Gen a) -> Gen a

Create a random generator which selects and executes a random generator from a non-empty array of random generators with uniform probability.

frequency :: forall a. NonEmptyList (Tuple Number (Gen a)) -> Gen a

Create a random generator which selects and executes a random generator from a non-empty, weighted list of random generators.

arrayOf :: forall a. Gen a -> Gen (Array a)

Create a random generator which generates an array of random values.

arrayOf1 :: forall a. Gen a -> Gen (NonEmptyArray a)

Create a random generator which generates a non-empty array of random values.

enum :: forall a. BoundedEnum a => Gen a

Create a random generator for a finite enumeration. toEnum i must be well-behaved: It must return a value wrapped in Just for all Ints between fromEnum bottom and fromEnum top.

listOf :: forall a. Int -> Gen a -> Gen (List a)

Create a random generator which generates a list of random values of the specified size.

vectorOf :: forall a. Int -> Gen a -> Gen (Array a)

Create a random generator which generates a vector of random values of a specified size.

elements :: forall a. NonEmptyArray a -> Gen a

Create a random generator which selects a value from a non-empty array with uniform probability.

shuffle :: forall a. Array a -> Gen (Array a)

Generate a random permutation of the given array

runGen :: forall a. Gen a -> GenState -> Tuple a GenState

Run a random generator

evalGen :: forall a. Gen a -> GenState -> a

Run a random generator, keeping only the randomly-generated result

perturbGen :: forall a. Number -> Gen a -> Gen a

Perturb a random generator by modifying the current seed

uniform :: Gen Number

A random generator which approximates a uniform random variable on [0, 1]

sample :: forall a. Seed -> Size -> Gen a -> Array a

Sample a random generator

randomSample :: forall a. Gen a -> Effect (Array a)

Get a random sample of 10 values. For a single value, use randomSampleOne.

randomSample' :: forall a. Size -> Gen a -> Effect (Array a)

Sample a random generator, using a randomly generated seed

randomSampleOne :: forall a. Gen a -> Effect a

Generate a single value using a randomly generated seed.