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Solonarv/mloeb.hs

Created December 11, 2020 19:03
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Monadic Loeb fixed-point combinator
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mloeb.hs
-- standard "loeb" combinator
-- https://github.com/quchen/articles/blob/master/loeb-moeb.md
loeb :: Functor f => f (f a -> a) -> f a
loeb x = go where go = fmap ($ go) x
-- "monadic loeb"?
loebM :: (Traversable t, Monad m) => t (t a -> m a) -> m (t a)
loebM = sequenceA . loeb . fmap (\f xs -> f =<< sequenceA xs)
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