32 lines
1022 B
Markdown
32 lines
1022 B
Markdown
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ordnub
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======
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Data.List.nub is O(n²). This one is O(n log n) by requiring an Ord instance.
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* Also contains a benchmark (`report.html`) that shows that `ordNub` apparently is faster than `nub` in *all* cases.
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* `PACKAGES_USING_NUB.txt` contains all packages which use `nub` (made with a quick grep).
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It's not the most accurate since some packages define their own `nub`, but that's a minority.
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**This thing here is not a library.** It is a benchmark suite. [View results here](http://htmlpreview.github.io/?https://github.com/nh2/haskell-ordnub/blob/master/report.html).
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Don't use nub
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-------------
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If you are looking for a fast `ordNub` function to use in your code, you can use:
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```haskell
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import qualified Data.Set as Set
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ordNub :: (Ord a) => [a] -> [a]
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ordNub l = go Set.empty l
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where
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go _ [] = []
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go s (x:xs) = if x `Set.member` s then go s xs
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else x : go (Set.insert x s) xs
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```
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### Other Data.List functions you NEVER want to use
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`\\`, `union`, `intersect`
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