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Add MonadThrow instance for Codensity #83

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Merged
RyanGlScott merged 1 commit into from
Sep 27, 2025
Merged

Add MonadThrow instance for Codensity #83

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1 change: 1 addition & 0 deletions kan-extensions.cabal
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Expand Up @@ -56,6 +56,7 @@ library
containers >= 0.4 && < 0.9,
contravariant >= 1 && < 2,
distributive >= 0.2.2 && < 1,
exceptions >= 0.10 && < 0.11,
invariant >= 0.1 && < 1,
free >= 4 && < 6,
mtl >= 2.2.1 && < 2.4,
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4 changes: 4 additions & 0 deletions src/Control/Monad/Codensity.hs
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Expand Up @@ -38,6 +38,7 @@ module Control.Monad.Codensity

import Control.Applicative
import Control.Monad (MonadPlus(..))
import Control.Monad.Catch (MonadThrow(..))
import qualified Control.Monad.Fail as Fail
import Control.Monad.Free
import Control.Monad.IO.Class
Expand Down Expand Up @@ -142,6 +143,9 @@ instance (v ~~ v', Alternative v')
instance (v ~~ v', Alternative v')
=> MonadPlus (Codensity (v :: k -> TYPE rep))

instance MonadThrow m => MonadThrow (Codensity m) where
throwM = lift . throwM

-- |
-- This serves as the *left*-inverse (retraction) of 'lift'.
--
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