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add ComonadStore instances for EnvT and TracedT #107

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Apr 7, 2018
Merged

add ComonadStore instances for EnvT and TracedT #107

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12 changes: 12 additions & 0 deletions src/Control/Comonad/Store/Class.purs
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Expand Up @@ -5,10 +5,14 @@ module Control.Comonad.Store.Class where
import Prelude

import Control.Comonad (class Comonad, extract)
import Control.Comonad.Env.Trans (EnvT)
import Control.Comonad.Store.Trans (StoreT(..))
import Control.Comonad.Traced.Trans (TracedT)
import Control.Comonad.Trans.Class (lower)
import Control.Extend (duplicate)

import Data.Tuple (Tuple(..))
import Data.Monoid (class Monoid)

-- | The `ComonadStore` type class represents those monads which support local position information via
-- | `pos` and `peek`.
Expand Down Expand Up @@ -52,3 +56,11 @@ seeks f = peeks f <<< duplicate
instance comonadStoreStoreT :: Comonad w => ComonadStore s (StoreT s w) where
pos (StoreT (Tuple f s)) = s
peek s (StoreT (Tuple f _)) = extract f s

instance comonadStoreEnvT :: ComonadStore s w => ComonadStore s (EnvT e w) where
pos = pos <<< lower
peek s = peek s <<< lower

instance comonadStoreTracedT :: (ComonadStore s w, Monoid m) => ComonadStore s (TracedT m w) where
pos = pos <<< lower
peek s = peek s <<< lower