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Add hoistDeclare #22

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d928083
Add `hoistDeclare`
masaeedu Apr 23, 2021
48063d6
Add missing import
masaeedu Apr 23, 2021
832b029
Add missing extension
masaeedu Apr 23, 2021
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12 changes: 12 additions & 0 deletions src/Data/OpenApi/Declare.hs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE UndecidableInstances #-}
{-# LANGUAGE RankNTypes #-}
-- |
-- Module: Data.OpenApi.Declare
-- Maintainer: Nickolay Kudasov <[email protected]>
Expand All @@ -28,7 +29,10 @@ import Control.Monad.Trans.RWS.Lazy as Lazy
import Control.Monad.Trans.RWS.Strict as Strict
import Control.Monad.Trans.Writer.Lazy as Lazy
import Control.Monad.Trans.Writer.Strict as Strict
import Control.Lens.Lens (Lens')
import Data.Functor.Identity
import Data.Functor.Compose
import Data.Tuple (swap)

-- | A declare monad transformer parametrized by:
--
Expand Down Expand Up @@ -115,6 +119,14 @@ execDeclareT (DeclareT f) d = fst <$> f d
undeclareT :: (Monad m, Monoid d) => DeclareT d m a -> m a
undeclareT = flip evalDeclareT mempty

-- | Lift a declaration-producing computation for a subpart into a
-- declaration-producing computation for the whole.
hoistDeclareT :: Functor m => Lens' d d' -> DeclareT d' m a -> DeclareT d m a
hoistDeclareT l = DeclareT . unconvert . l . convert . runDeclareT
where
convert f = Compose . fmap swap . f
unconvert f = fmap swap . getCompose . f

-- | A declare monad parametrized by @d@ — the output to accumulate (declarations).
--
-- This monad is similar to both state and writer monads.
Expand Down