Assorted concrete container types

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LTS Haskell 22.30:0.6.7
Stackage Nightly 2024-07-24:0.6.8
Latest on Hackage:0.7

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BSD-3-Clause licensed
Maintained by [email protected]
This version can be pinned in stack with:containers-,7299

This package contains efficient general-purpose implementations of various basic immutable container types. The declared cost of each operation is either worst-case or amortized, but remains valid even if structures are shared.


Changelog for containers package Dec 2015

  • Planned to bundle with GHC 8.0.1.

  • Add IsString instance to Data.Sequence.

  • Define Semigroup instances for ``Data.Map, Data.Set`, `Data.IntMap`, `Data.IntSet` and `Data.Sequence`. Dec 2014

  • Bundled with GHC 7.10.1.

  • Add role annotations for Data.Map and Data.Set.

  • Add IsList instances for Data.Map, Data.Set, Data.IntMap and Data.IntSet.

  • Several performance improvements for Data.Sequence.

  • Add Data.Sequence.fromFunction and Data.Sequence.fromArray. Jan 2014

  • Bundled with GHC 7.8.1.

  • The Data.Map.fromList and Data.Set.fromList now use linear-time algorithm if the input is sorted, without need to call fromDistinctAscList.

  • Implement indexing operations (lookupIndex, findIndex, elemAt, deletaAt) for Data.Set too.

  • Add Applicative and Alternative instances for Data.Sequence.

  • Add foldMapWithKey to Data.Map and Data.IntMap.

  • Implement poly-kinded Typeable.

  • Add Functor instance for Data.Graph.SCC.

  • Add Data.Map.splitRoot and Data.Set.splitRoot. May 2012

  • Bundled with GHC 7.6.1.

  • Major improvements since last release:

    • a clearer distinction between value-lazy and value-strict containers,
    • performance improvements across the board,
    • a big internal clean-up, and
    • new functions for e.g. merging, updating, and searching containers.
  • While the old Data.Map and Data.IntMap modules will continue to exist for the foreseeable future, we’ve abandoned the practice of having the strict and lazy versions of each function distinguished by an apostrophe. The distinction is instead made at the module level, by introducing four new modules:

    • Data.Map.Strict
    • Data.Map.Lazy
    • Data.IntMap.Strict
    • Data.IntMap.Lazy

    This split has three benefits:

    • It makes the choice between value-strict and value-lazy containers more declarative; you pick once at import time, instead of having to remember to use the strict or lazy versions of a function every time you modify the container.
    • It alleviates a common source of performance issues, by forcing the user to think about the strictness properties upfront. For example, using insertWith instead of insertWith’ is a common source of containers-related performance bugs.
    • There are fewer functions per module, making it easier to get an overview of each module.
  • Note that the types used in the strict and lazy APIs are the same, so you can still use the same container in a “mixed” manner, if needed.

  • The Data.IntSet representation changed to store small sets using bits in an Word. Larger sets are stored as a collection of such dense small sets, connected together by a prefix trie. Feb 2012

  • Bundled with GHC 7.4.1.

  • Data.Map now exports foldr, foldr’, foldlandfoldl’`.

  • Data.Set now exports foldr, foldr’, foldlandfoldl’`.

  • Data.IntMap now exports foldr, foldr’, foldl, foldl’, foldrWithKey, foldrWithKey’, foldlWithKeyandfoldlWithKey’`.

  • Data.IntSet now exports foldr, foldr’, foldlandfoldl’`.

  • Data.Map.foldWithKey is no longer deprecated, although it is expected to be deprecated again in the future.

  • There are now NFData instance for Data.Map.Map, Data.Set.Set, Data.IntMap.IntMap, Data.IntSet.IntSet and Data.Tree.Tree. Aug 2011

  • Bundled with GHC 7.2.1.

  • Data.Map now exports new functions foldrWithKey' and foldlWithKey', which are strict variants of foldrWithKey and foldlWithKey respectively.

  • Data.IntMap now exports new functions insertWith' and insertWithKey', which are strict variants of insertWith and insertWithKey respectively. Nov 2010

  • Bundled with GHC 7.0.1.

  • Strictness is now more consistent, with containers being strict in their elements even in singleton cases.

  • There is a new function insertLookupWithKey' in Data.Map.

  • The foldWithKey function in Data.Map has been deprecated in favour of foldrWithKey. Dec 2009

  • Bundled with GHC 6.12.1.

  • mapAccumRWithKey has been added to Data.IntMap.

  • A Traversable instance has been added to Data.IntMap.IntMap.

  • The types of Data.IntMap.intersectionWith and Data.IntMap.intersectionWithKey have been changed from intersectionWith :: (a -> b -> a) -> IntMap a -> IntMap b -> IntMap a intersectionWithKey :: (Key -> a -> b -> a) -> IntMap a -> IntMap b -> IntMap a to intersectionWith :: (a -> b -> c) -> IntMap a -> IntMap b -> IntMap c intersectionWithKey :: (Key -> a -> b -> c) -> IntMap a -> IntMap b -> IntMap c

  • The types of Data.IntMap.findMin and Data.IntMap.findMax have been changed from findMin :: IntMap a -> a findMax :: IntMap a -> a to findMin :: IntMap a -> (Int,a) findMax :: IntMap a -> (Int,a)

  • Data.Map now exports mapAccumRWithKey, foldrWithKey, foldlWithKey and toDescList.

  • Data.Sequence now exports replicate, replicateA, replicateM, iterateN, unfoldr, unfoldl, scanl, scanl1, scanr, scanr1, tails, inits, takeWhileL, takeWhileR, dropWhileL, dropWhileR, spanl, spanr, breakl, breakr, partition, filter, sort, sortBy, unstableSort, unstableSortBy, elemIndexL, elemIndicesL, elemIndexR, elemIndicesR, findIndexL, findIndicesL, findIndexR, findIndicesR, foldlWithIndex, foldrWithIndex, mapWithIndex, zip, zipWith, zip3, zipWith3, zip4 and zipWith4. Nov 2008

  • Bundled with GHC 6.10.1.

  • Various result type now use Maybe rather than allowing any Monad. Nov 2007

  • Bundled with GHC 6.8.1.

  • Initial split off from GHC base.