----------------------------------------------------------------------------- -- | -- Module : Data.Barbie -- -- Support for operating on Barbie-types with constrained functions. -- -- Consider the following function: -- -- @ -- showIt :: 'Show' a => 'Maybe' a -> 'Data.Functor.Const' 'String' a -- showIt = 'Data.Functor.Const' . 'show' -- @ -- -- We would then like to be able to do: -- -- @ -- 'Data.Barbie.bmap' 'showIt' :: 'Data.Barbie.FunctorB' b => b 'Maybe' -> b ('Data.Functor.Const' 'String') -- @ -- -- This however doesn't work because of the @('Show' a)@ constraint in the -- the type of @showIt@. -- -- This module adds support to overcome this problem. ---------------------------------------------------------------------------- module Data.Barbie.Constraints ( -- * Proof of instance DictOf(..) , packDict , requiringDict -- * Retrieving proofs , ConstraintsB(ConstraintsOf) , ProofB(..) ) where import Data.Barbie.Internal.Constraints import Data.Barbie.Internal.Dicts import Data.Barbie.Internal.ProofB