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-- General utilities:
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-- | '<$$>': alias for composition of fmap with itself.
(<$$>) :: (Functor f, Functor g) => (a -> b) -> f (g a) -> f (g b)
(<$$>) = (<$>) . (<$>)
(<$$>) :: (Functor f, Functor g) => (a -> b) -> f (g a) -> f (g b)
(<$$>) = (<$>) . (<$>)
(<$$>) = (<$>) . (<$>)