Data.Unfolder

Unfolders provide a way to unfold data structures. They are basically Alternative instances, but the choose method allows the unfolder to do something special for the recursive positions of the data structure.

Unfolder

class Alternative f => Unfolder f where

Unfolders provide a way to unfold data structures. The methods have default implementations in terms of Alternative, but you can implement choose to act on recursive positions of the data structure, or simply to provide a faster implementation than asum.

Methods

choose :: [f x] -> f x

Choose one of the values from the list.

chooseInt :: Int -> f Int

Given a number n, return a number between '0' and 'n - 1'.

Instances

Unfolder []

Don't choose but return all items.

Unfolder Maybe

Always choose the first item.

Unfolder Arb

Limit the depth of the generated data structure by dividing the given size by the number of recursive positions.

MonadPlus m => Unfolder (WrappedMonad m)

Derived instance.

Unfolder f => Unfolder (Reverse f)

Derived instance.

Unfolder f => Unfolder (Backwards f)

Derived instance.

Unfolder f => Unfolder (Lift f)

Derived instance.

(Functor m, Monad m) => Unfolder (MaybeT m)

Derived instance.

Applicative f => Unfolder (ListT f)

Derived instance.

Applicative f => Unfolder (BFS f)

Choose between values of a given depth only.

Unfolder f => Unfolder (DualA f)

Reverse the list passed to choose.

(ArrowZero a, ArrowPlus a) => Unfolder (WrappedArrow a b)

Derived instance.

(Monoid w, Unfolder m) => Unfolder (WriterT w m)

Derived instance.

(MonadPlus m, Unfolder m) => Unfolder (StateT s m)

Derived instance.

Unfolder m => Unfolder (ReaderT r m)

Derived instance.

(Functor m, Monad m, Error e) => Unfolder (ErrorT e m)

Derived instance.

(Unfolder p, Applicative q) => Unfolder (Compose p q)

Derived instance.

(Unfolder p, Unfolder q) => Unfolder (Product p q)

Derived instance.

(Functor m, Monad m, RandomGen g) => Unfolder (Random g m)

Choose randomly.

(Monoid w, MonadPlus m, Unfolder m) => Unfolder (RWST r w s m)

Derived instance.

chooseMonadDefault :: (Monad m, Unfolder m) => [m x] -> m x

If an unfolder is monadic, choose can be implemented in terms of chooseInt.

boundedEnum :: forall f a. (Unfolder f, Bounded a, Enum a) => f a

If a datatype is bounded and enumerable, we can use chooseInt to generate a value.

Unfolder instances

newtype DualA f a

DualA flips the '(|)' operator.

Constructors

DualA

Fields

getDualA :: f a

Instances

Functor f => Functor (DualA f)

Applicative f => Applicative (DualA f)

Alternative f => Alternative (DualA f)

Unfolder f => Unfolder (DualA f)

Reverse the list passed to choose.

newtype Random g m a

Constructors

Random

Fields

getRandom :: StateT g m a

Instances

Monad m => Monad (Random g m)

Functor m => Functor (Random g m)

(Functor m, Monad m, RandomGen g) => MonadPlus (Random g m)

(Monad m, Functor m) => Applicative (Random g m)

(Functor m, Monad m, RandomGen g) => Alternative (Random g m)

(Functor m, Monad m, RandomGen g) => Unfolder (Random g m)

Choose randomly.

newtype BFS f x

Return a generator of values of a given depth. Returns Nothing if there are no values of that depth or deeper. The depth is the number of choose calls.

Constructors

BFS

Fields

getBFS :: Int -> Maybe [f x]

Instances

Functor f => Functor (BFS f)

Applicative f => Applicative (BFS f)

Applicative f => Alternative (BFS f)

Applicative f => Unfolder (BFS f)

Choose between values of a given depth only.

runBFS :: Unfolder f => BFS f x -> f x

packBFS :: f x -> BFS f x

data Arb a

A variant of Test.QuickCheck.Gen, with failure and a count of the number of recursive positions.

Constructors

Arb Int (StdGen -> Int -> Maybe a)

Instances

Functor Arb

Applicative Arb

Alternative Arb

Unfolder Arb

Limit the depth of the generated data structure by dividing the given size by the number of recursive positions.

arbUnit :: Arbitrary a => Arb a