Data.Utils.Random

This module provides utilities for working with module Random.

Documentation

pickR' :: MonadRandom m => [a] -> m (a, [a])

Picks a random element of the list and returns that element and the remaining elements.

>>> evalRand (pickR' "Haskell") (mkStdGen 4712)
('s',"Hakell")

pickR :: MonadRandom m => [a] -> m a

Picks a random element of the list.

>>> evalRand (pickR "Haskell") (mkStdGen 4712)
's'

takeR' :: forall m a. MonadRandom m => Int -> [a] -> m ([a], [a])

Takes the specified number of random elements from the list. Returns those elements and the remaining elements.

>>> evalRand (takeR' 3 "Haskell") (mkStdGen 4712)
("aks","Hell")

takeR :: MonadRandom m => Int -> [a] -> m [a]

Takes the specified number of random elements from the list.

>>> evalRand (takeR 3 "Haskell") (mkStdGen 4712)
"aks"

fisherYates :: forall m a. MonadRandom m => Array Int a -> m (Array Int a)

Shuffles an array with the Fisher-Yates algorithm.

shuffleR :: MonadRandom m => [a] -> m [a]

Shuffles an list with the Fisher-Yates algorithm.

>>> evalRand (shuffleR "Haskell") (mkStdGen 4712)
"skalHle"

boxMuller :: forall m a. (Floating a, Random a, Eq a, MonadRandom m) => m a

Uses the Box-Muller transform to sample the standard normal distribution (zero expectation, unit variance).

>>> evalRand (replicateM 5 boxMuller) (mkStdGen 1234) :: [Float]
[0.61298496,-0.19325614,4.4974413e-2,-0.31926495,-1.1109064]

boxMuller' :: (Floating a, Random a, Eq a, MonadRandom m) => a -> a -> m a

Uses the Box-Muller transform to sample a normal distribution with specified mean and stadard deviation.

>>> evalRand (replicateM 5 $ boxMuller' 10 2) (mkStdGen 1234) :: [Float]
[11.22597,9.613487,10.089949,9.36147,7.7781873]

roulette :: forall a b m. (Ord b, Fractional b, Random b, MonadRandom m) => Int -> [(a, b)] -> m [a]

Randomly selects the specified number of elements of a weighted list.

>>> evalRand (roulette 10 [('x', 1 :: Double), ('y', 2)]) (mkStdGen 1000)
"yxxyyyyxxy"