Documentation

Init.Data.Random

Basic random number generator support based on the one available on the Haskell library

class RandomGen (g : Type u) :

Interface for random number generators.

  • range : gNat × Nat

    range returns the range of values returned by the generator.

  • next : gNat × g

    next operation returns a natural number that is uniformly distributed the range returned by range (including both end points), and a new generator.

  • split : gg × g

    The 'split' operation allows one to obtain two distinct random number generators. This is very useful in functional programs (for example, when passing a random number generator down to recursive calls).

Instances
structure StdGen :

"Standard" random number generator.

Instances For
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The range of values returned by StdGen

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The next value from a StdGen, paired with an updated generator state.

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Splits a StdGen into two separate states.

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def mkStdGen (s : Nat := 0) :

Returns a standard number generator.

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  • mkStdGen s = { s1 := s % 2147483562 + 1, s2 := s / 2147483562 % 2147483398 + 1 }
def randNat {gen : Type u} [RandomGen gen] (g : gen) (lo hi : Nat) :
Nat × gen

Generates a random natural number in the interval [lo, hi].

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def randBool {gen : Type u} [RandomGen gen] (g : gen) :
Bool × gen

Generates a random Boolean.

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Seeds the random number generator state used by IO.rand.

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def IO.rand (lo hi : Nat) :

Returns a pseudorandom number between lo and hi, using and updating a saved random generator state.

This state can be seeded using IO.setRandSeed.

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