containers-0.5.9.2: changelog.md

# Changelog for [`containers` package](http://github.com/haskell/containers)

## 0.5.9.2

* Fix completely broken implementations of `restrictKeys` and `withoutKeys`
in `Data.IntMap`.

* Fix minor bug in `Show1` instance for `Data.Tree`.

* Fix broken documentation links.

## 0.5.9.1

* Add `merge` and `mergeA` for `Data.IntMap`.

* Add instances for `Data.Graph.SCC`: `Foldable`, `Traversable`, `Data`,
  `Generic`, `Generic1`, `Eq`, `Eq1`, `Show`, `Show1`, `Read`, and `Read1`.

* Add lifted instances (from `Data.Functor.Classes`) for `Data.Sequence`,
  `Data.Map`, `Data.Set`, `Data.IntMap`, and `Data.Tree`. (Thanks to
  Oleg Grenrus for doing a lot of this work.)

* Properly deprecate functions in `Data.IntMap` long documented as deprecated.

* Rename several internal modules for clarity. Thanks to esoeylemez for starting
  this process.

* Make `Data.Map.fromDistinctAscList` and `Data.Map.fromDistinctDescList` more
  eager, improving performance.

* Plug space leaks in `Data.Map.Lazy.fromAscList` and
 `Data.Map.Lazy.fromDescList` by manually inlining constant functions.

* Add `lookupMin` and `lookupMax` to `Data.Set` and `Data.Map` as total
alternatives to `findMin` and `findMax`.

* Add `!?` to `Data.Map` as a total alternative to `!`.

* Avoid using `deleteFindMin` and `deleteFindMax` internally, preferring
total functions instead. New implementations of said functions lead to slight
performance improvements overall.

## 0.5.8.1 *Aug 2016*

### General package changes

  * Remove all attempts to support nhc98 and any versions of GHC
    before 7.0.

  * Integrate benchmarks with Cabal. (Thanks, Gabriel Gonzalez!)
  
  * Make Cabal report required extensions properly, and stop using
    default extensions. Note that we do *not* report extensions conditionally enabled
    based on GHC version, as doing so would lead to a maintenance nightmare
    with no obvious benefits.

  * Use `BangPatterns` throughout to reduce noise. This extension
    is now *required* to compile `containers`.

  * Improve QuickCheck properties taking arbitrary functions by using
    `Test.QuickCheck.Function.Fun` instead of evil `Show` instances
    for functions.

  * Expose several internal modules through Cabal (as requested by
    Edward Kmett). These remain completely unsupported.

### New exports and instances

  * Add `alterF`, `restrictKeys`, and `withoutKeys` to `Data.Map`
    and `Data.IntMap`.

  * Add `take`, `drop`, `splitAt`, `takeWhileAntitone`, `dropWhileAntitone`,
    and `spanAntitone` for `Data.Map` and `Data.Set`. Thanks to Cale Gibbard
    for suggesting these.

  * Add `merge`, `mergeA`, and associated merge tactics for `Data.Map`.
    Many thanks to Cale Gibbard, Ryan Trinkle, and Dan Doel for
    inspiring the merge idea and helping refine the interface.

  * Add `fromDescList`, `fromDescListWith`, `fromDescListWithKey`,
    and `fromDistinctDescList` to `Data.Map`.

  * Add `fromDescList` and `fromDistinctDescList` to `Data.Set`.

  * Add `Empty`, `:<|`, and `:|>` pattern synonyms for `Data.Sequence`.

  * Add `adjust'`, `(!?)`, `lookup`, `chunksOf`, `cycleTaking`, `insertAt`, `deleteAt`, `intersperse`,
    `foldMapWithIndex`, and `traverseWithIndex` for `Data.Sequence`.

  * Derive `Generic` and `Generic1` for `Data.Tree.Tree`, `Data.Sequence.ViewL`,
    and `Data.Sequence.ViewR`.

  * Add `foldTree` for `Data.Tree`. (Thanks, Daniel Wagner!)

### Semantic changes

  * Make `Data.Sequence.splitAt` strict in its arguments. Previously,
    it returned a lazy pair.

  * Fix completely erroneous definition of `length` for `Data.Sequence.ViewR`.
  
  * Make `Data.Map.Strict.traverseWithKey` force result values before
    installing them in the new map.

  * Make `drawTree` handle newlines better. (Thanks, recursion-ninja!)

### Deprecations

  * All functions in `Data.Map` proper that have been documented as deprecated since
    version 0.5 or before now have `DEPRECATED` pragmas and will actually be
    removed after another cycle or two.

  * Tree printing functions in `Data.Map` intended for library debugging are now
    deprecated. They will continue to be available for the foreseeable future in
    an internal module.

### Performance changes

  * Substantially speed up `splitAt`, `zipWith`, `take`, `drop`,
    `fromList`, `partition`, `foldl'`, and `foldr'` for `Data.Sequence`.
    Special thanks to Lennart Spitzner for digging into the performance
    problems with previous versions of `fromList` and finding a way to
    make it really fast. Slightly optimize `replicateA`. Stop `traverse`
    from performing many unnecessary `fmap` operations.

  * Most operations in `Data.Sequence` advertised as taking logarithmic
    time (including `><` and `adjust`) now use their full allotted time
    to avoid potentially building up chains of thunks in the tree. In general,
    the only remaining operations that avoid doing more than they
    really need are the particular bulk creation and transformation functions
    that really benefit from the extra laziness. There are some situations
    where this change may slow programs down, but I think having more
    predictable and usually better performance more than makes up for that.

  * Add rewrite rules to fuse `fmap` with `reverse` for `Data.Sequence`.

  * Switch from *hedge* algorithms to *divide-and-conquer* algorithms
    for union, intersection, difference, and merge in both `Data.Map`
    and `Data.Set`. These algorithms are simpler, are known to be
    asymptotically optimal, and are faster according to our benchmarks.

  * Speed up `adjust` for `Data.Map`. Allow `map` to inline, and
    define a custom `(<$)`. This considerably improves mapping with
    a constant function.

  * Remove non-essential laziness in `Data.Map.Lazy` implementation.

  * Speed up deletion and alteration functions for `Data.IntMap`.


## 0.5.7.1  *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`.

## 0.5.6.2  *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`.

## 0.5.4.0  *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`.

## 0.5.0.0  *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.

## 0.4.2.1  *Feb 2012*

  * Bundled with GHC 7.4.1.

  * `Data.Map now exports `foldr`, `foldr'`, `foldl` and `foldl'`.

  * `Data.Set now exports `foldr`, `foldr'`, `foldl` and `foldl'`.

  * `Data.IntMap now exports `foldr`, `foldr'`, `foldl`, `foldl'`, `foldrWithKey`, `foldrWithKey'`, `foldlWithKey` and `foldlWithKey'`.

  * `Data.IntSet now exports `foldr`, `foldr'`, `foldl` and `foldl'`.

  * `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`.

## 0.4.1.0  *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.

## 0.4.0.0  *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`.

## 0.3.0.0  *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`.

## 0.2.0.0  *Nov 2008*

  * Bundled with GHC 6.10.1.

  * Various result type now use `Maybe` rather than allowing any `Monad`.

## 0.1.0.0  *Nov 2007*

  * Bundled with GHC 6.8.1.

  * Initial split off from GHC base.