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Should firstTraversing and leftTraversing be defined in terms of wander? #48

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treeowl opened this issue Apr 2, 2017 · 0 comments

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treeowl commented Apr 2, 2017

Currently,

firstTraversing :: Traversing p => p a b -> p (a, c) (b, c)
firstTraversing = dimap swap swap . traverse'

leftTraversing :: Traversing p => p a b -> p (Either a c) (Either b c)
leftTraversing = dimap swapE swapE . traverse'

Would it be better or worse to use wander, or the same?

firstTraversing = wander $ \afb (a,c) -> (\a' -> (a', c)) <$> afb a
leftTraversing = wander $ \afb -> either (fmap Left . afb) (pure . Right)

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