A typeclass for monads with a chosen source of entropy. For example, RVar is such a monad - the source from which it is (eventually) sampled is the only source from which a random variable is permitted to draw, so when directly requesting entropy for a random variable these functions are used.

Minimum implementation is either the internal getRandomPrim or all other functions. Additionally, this class's interface is subject to extension at any time, so it is very, very strongly recommended that the monadRandom Template Haskell function be used to implement this function rather than directly implementing it. That function takes care of choosing default implementations for any missing functions; as long as at least one function is implemented, it will derive sensible implementations of all others.

To use monadRandom, just wrap your instance declaration as follows (and enable the TemplateHaskell and GADTs language extensions):

$(monadRandom [d|
        instance MonadRandom FooM where
            getRandomDouble = return pi
            getRandomWord16 = return 4
            {- etc... -}
    |])

A source of entropy which can be used in the given monad.

See also MonadRandom.

Minimum implementation is either the internal getRandomPrimFrom or all other functions. Additionally, this class's interface is subject to extension at any time, so it is very, very strongly recommended that the randomSource Template Haskell function be used to implement this function rather than directly implementing it. That function takes care of choosing default implementations for any missing functions; as long as at least one function is implemented, it will derive sensible implementations of all others.

To use randomSource, just wrap your instance declaration as follows (and enable the TemplateHaskell, MultiParamTypeClasses and GADTs language extensions, as well as any others required by your instances, such as FlexibleInstances):

$(randomSource [d|
        instance RandomSource FooM Bar where
            {- at least one RandomSource function... -}
    |])

Complete a possibly-incomplete Context implementation. It is recommended that this macro be used even if the implementation is currently complete, as the Context class may be extended at any time.

To use monadRandom, just wrap your instance declaration as follows (and enable the TemplateHaskell and GADTs language extensions):

$(monadRandom [d|
        instance MonadRandom FooM where
            getRandomDouble = return pi
            getRandomWord16 = return 4
            {- etc... -}
    |])

Complete a possibly-incomplete Context implementation. It is recommended that this macro be used even if the implementation is currently complete, as the Context class may be extended at any time.

To use randomSource, just wrap your instance declaration as follows (and enable the TemplateHaskell, MultiParamTypeClasses and GADTs language extensions, as well as any others required by your instances, such as FlexibleInstances):

$(randomSource [d|
        instance RandomSource FooM Bar where
            {- at least one RandomSource function... -}
    |])