module Data.Constraint.Unsafe
( evil
, derive
, underive
, applicative
, alternative
) where
import Control.Applicative
import Control.Monad
import Control.Newtype
import Data.Constraint
import Unsafe.Coerce
evil :: a :- b
evil = unsafeCoerce refl
derive :: Newtype n o => (o -> n) -> t o :- t n
derive _ = evil
underive :: Newtype n o => (o -> n) -> t n :- t o
underive _ = evil
applicative :: forall m a. Monad m => (Applicative m => m a) -> m a
applicative m = m \\ trans (evil :: Applicative (WrappedMonad m) :- Applicative m) ins
alternative :: forall m a. MonadPlus m => (Alternative m => m a) -> m a
alternative m = m \\ trans (evil :: Alternative (WrappedMonad m) :- Alternative m) ins