Implement and test Foldable/Traversable instances#16
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thomashoneyman merged 5 commits intopurescript:masterfrom Feb 10, 2022
MaybeJustJames:foldable-instance
Merged
Implement and test Foldable/Traversable instances#16thomashoneyman merged 5 commits intopurescript:masterfrom MaybeJustJames:foldable-instance
thomashoneyman merged 5 commits intopurescript:masterfrom
MaybeJustJames:foldable-instance
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Thanks! cc @colinwahl, as we were just working through this library together — do you have any thoughts? |
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I have a followup with |
JordanMartinez
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Feb 10, 2022
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I'd say add it here. |
src/Data/Graph.purs
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| instance foldableGraph :: Foldable (Graph k) where | ||
| foldl f z (Graph m) = foldl f z $ fst <$> M.values m | ||
| foldr f z (Graph m) = foldr f z $ fst <$> M.values m | ||
| foldMap f (Graph m) = foldMap f $ fst <$> M.values m |
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Ideally, we would use 1 fold rather than 2 here (i.e. M.values folds once, then <$> folds a second time). But the single fold version...
foldl f z (foldl (\acc (Tuple k _) -> Array.snoc acc k) [] m)
... is likely less performant because of the usage of Array.snoc.
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Would something like this be better?
instance foldableGraph :: Foldable (Graph k) where
foldl f z (Graph m) = foldl (\acc (Tuple k _) -> f acc k) z $ M.values m
foldr f z (Graph m) = foldr (\(Tuple k _) acc -> f k acc) z $ M.values m
foldMap f (Graph m) = foldMap (f <<< fst) $ M.values mThanks for help from @mikesol
JordanMartinez
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JordanMartinez
approved these changes
Feb 10, 2022
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@thomashoneyman Yep, looks fine to me! |
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Implement a
Foldableinstance forGraph.Checklist: