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Define a convenience to unwrap and project.

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This commit is contained in:
Rob Rix 2017-03-26 18:03:27 -04:00
parent 76218f1b9f
commit 2ab72ea378
1 changed files with 4 additions and 0 deletions
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src/Data/Functor/Union.hs
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@ -13,6 +13,10 @@ data Union (ts :: [* -> *]) (a :: *) where
wrapU :: (MonadFree (Union fs) m, InUnion fs f) => f (m a) -> m a
wrapU = wrap . emb
-- | Unwrap a cofree comonad and project a functor from the resulting union.
unwrapU :: (ComonadCofree (Union fs) w, InUnion fs f) => w a -> Maybe (f (w a))
unwrapU = proj . unwrap
-- Classes