generic-random
Generic random generators
http://github.com/lysxia/generic-random
| Version on this page: | 1.1.0.2@rev:1 |
| LTS Haskell 23.19: | 1.5.0.1 |
| Stackage Nightly 2025-04-30: | 1.5.0.1 |
| Latest on Hackage: | 1.5.0.1 |
Maintained by [email protected]
This version can be pinned in stack with:
generic-random-1.1.0.2@sha256:7315cdf13c60b25d3087955c9bbe5ebaf7953b17f75b9a7120d0eea654d712e2,1493Module documentation for 1.1.0.2
- Generic
Depends on 2 packages(full list with versions):
Generic random generators 
Derive simple random generators for QuickCheck using generics.
Automating the Arbitrary boilerplate also ensures that if a type changes to
have more constructors, then the generator fixes itself to generate that new
case (with uniform distribution) or causes a compilation error (with an
explicit distribution).
A simple (optional) strategy to ensure termination for recursive types:
make Test.QuickCheck.Gen’s size parameter decrease at every recursive call;
when it reaches zero, sample directly from a trivially terminating generator
given explicitly (genericArbitraryRec and withBaseCase) or implicitly
(genericArbitrary').
Example
{-# LANGUAGE DeriveGeneric #-}
import GHC.Generics (Generic)
import Test.QuickCheck
import Generic.Random
data Tree a = Leaf | Node (Tree a) a (Tree a)
deriving (Show, Generic)
instance Arbitrary a => Arbitrary (Tree a) where
arbitrary = genericArbitraryRec uniform `withBaseCase` return Leaf
-- Equivalent to
-- > arbitrary =
-- > sized $ \n ->
-- > if n == 0 then
-- > return Leaf
-- > else
-- > oneof
-- > [ return Leaf
-- > , resize (n `div` 3) $
-- > Node <$> arbitrary <*> arbitrary <*> arbitrary
-- > ]
main = sample (arbitrary :: Gen (Tree ()))