Add generic foldMap #337
Add generic foldMap #337
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Looks good to me. I don't think we need to dwell too much on explaining these functions since this is the concept from |
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I'd like to keep this PR for a few days. Maybe I'll come with something better. It's well known concept but I think it worth repeating |
Data/Vector.hs
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| -- | @since NEXT | ||
| -- /O(n)/ Map each element of the structure to a monoid, and combine | ||
| -- the results. This function is implemented in terms of 'foldr' in | ||
| -- the same way as default implementation in 'Foldable' type class. |
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We could avoid refering to implementation details by saying "Map each element of the structure to a monoid, and combine results {lazily,strictly}, similar to Data.Foldable.{foldMap,foldMap'}" or along these lines.
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At first I removed foldl/foldr mentions as implementation detial. But then decided to restore it. Whether function will fuse or not depends whether foldl/foldr is used. It's unfortunate that implementation details leak like that
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I tried and failed to come up with anything better. So I think PR is ready for merge |
Data/Vector/Generic.hs
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| foldMap' f = foldl' (\acc a -> acc `mappend` f a) mempty | ||
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This is a very minor nitpicking, but you put three empty lines here, two empty lines in Data.Vector and one line elsewhere.
Co-authored-by: Bodigrim <andrew.lelechenko@gmail.com>
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@Bodigrim fixed everything you mentioned |
Co-authored-by: Bodigrim <andrew.lelechenko@gmail.com>
Fixes #263.
foldMapis implemented in terms offoldrandfoldMap'in terms offoldl'This is draft since I want to make sure that we agree on implementation and documentation and only then do copy-paste work. I certainly don't like haddocks as wrote them. Those are riddles fit for sphinx.
foldMapis useful when one do need laziness but I can't put in words. Suggestions?