Control.Monad.Dep.SimpleAdvice.Basic

This module contains basic examples advices.

BEWARE! These are provided for illustrative purposes only, they strive for simplicity and not robustness or efficiency.

Basic advices

returnMempty :: forall ca m r. (Monad m, Monoid r) => Advice ca m r

Makes functions discard their result and always return mempty.

printArgs :: forall m r. MonadIO m => Handle -> String -> Advice Show m r

Given a Handle and a prefix string, makes functions print their arguments to the Handle.

data AnyEq where

A helper datatype for universal equality comparisons of existentialized values, used by doCachingBadly.

For a more complete elaboration of this idea, see the the "exinst" package.

Constructors

AnyEq :: forall a. (Typeable a, Eq a) => a -> AnyEq

Instances

Eq AnyEq

Defined in Control.Monad.Dep.SimpleAdvice.Basic

Methods

(==) :: AnyEq -> AnyEq -> Bool

(/=) :: AnyEq -> AnyEq -> Bool

doCachingBadly :: forall m r. Monad m => (AnyEq -> m (Maybe r)) -> (AnyEq -> r -> m ()) -> Advice (Eq `And` Typeable) m r

Given the means for looking up and storing r values in the underlying monad m, makes functions (inefficiently) cache their results.

The monad m and the result type r must be known before building the advice. So, once built, this Advice won't be polymorphic over them.

The implementation of this function makes use of the existential type parameter u of makeAdvice, because the phase that processes the function arguments needs to communicate the calculated AnyEq cache key to the phase that processes the function result.

A better implementation of this advice would likely use an AnyHashable helper datatype for the keys.

doAsyncBadly :: forall ca m. MonadUnliftIO m => Advice ca m ()

Makes functions that return () launch asynchronously.

A better implementation of this advice would likely use the "async" package instead of bare forkIO.

The IO monad could be generalized to MonadUnliftIO.