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paulp/monad.hs

Created August 23, 2018 06:42
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  1. paulp created this gist Aug 23, 2018.
    4 changes: 4 additions & 0 deletions monad.hs
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    Original file line number Diff line number Diff line change
    @@ -0,0 +1,4 @@
    instance Monad f => Monad (OptionalT f) where
    f =<< x = OptionalT $ runOptionalT x >>= \case
    Empty -> return Empty
    Full a -> runOptionalT $ f a