generic-random-1.0.0.0: README.md

Generic random generators [![Hackage](https://img.shields.io/hackage/v/generic-random.svg)](https://hackage.haskell.org/package/generic-random) [![Build Status](https://travis-ci.org/Lysxia/generic-random.svg)](https://travis-ci.org/Lysxia/generic-random)
=========================

Derive simple random generators for [QuickCheck](https://hackage.haskell.org/package/QuickCheck) using generics.

Example
-------

```haskell
    {-# 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 ()))
```

Features
--------

- User-specified distribution of constructors.
- A simple (optional) strategy to ensure termination for recursive types:
  using `genericArbitrary'`, `Test.QuickCheck.Gen`'s size parameter decreases
  at every recursive call; when it reaches zero, sample directly from a
  trivially terminating generator.