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haskell/containers

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Is haskell/containers beginner-friendly?

We have not seen enough recent pull requests from outside contributors to haskell/containers to say how often they are merged. 1 beginner-friendly issue is open now.

Stars
355
Forks
194
Open beginner issues
1
Indexed issues
103
Avg merge
2d 6h
Merged PRs (30d)
5
Dominant language
Haskell
License
No license data
Last GitHub push
Sep 20, 2026
Latest indexed
Sep 14, 2026
Contributing guide
No code of conduct
Beginner labels
No beginner labels indexed

How to contribute to haskell/containers

  1. Read the contributing guide first: it says how the maintainers want changes proposed, tested and reviewed.
  2. Pick the open beginner-friendly issue below and comment that you want to work on it before you start.
Beginner friendly Everything
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Issues somebody may already be working on are listed last. List everything by date

  • Strict prefix/lazy suffix for states?
    Open
    • Is something wrong?

    Difficulty 5/5 Over a week Newbie friendliness 35/100

    haskell/containers#1261 · 5 comments ·

  • unfoldTree is too lazy
    Open
    • Is something wrong?
    major-release strictness Tree

    Difficulty 2/5 1-3 hours Newbie friendliness 72/100

    haskell/containers#1260 ·

  • IntSet's minView and maxView creates unwanted thunks
    Open
    • Is something wrong?
    IntSet low-hanging-fruit performance

    Difficulty 3/5 1-2 days Newbie friendliness 58/100

    haskell/containers#1251 ·

  • Drop GHC 8.2/base-4.10 in next major release
    Open
    • Is something wrong?
    maintainability major-release

    Difficulty 3/5 1-2 days Newbie friendliness 70/100

    haskell/containers#1250 ·

  • PostOrder: foldl and foldr'
    Open
    • Is something wrong?
    performance Tree

    Difficulty 3/5 1-2 days Newbie friendliness 55/100

    haskell/containers#1247 ·

  • `IntSet.difference`: SpecConstr reboxing defeats the `NOM -> t1` sharing at -O2
    Open
    • Is something wrong?

    Difficulty 4/5 3-5 days Newbie friendliness 50/100

    haskell/containers#1242 ·

  • IntMap.delete allocates even for absent keys
    Open
    • Is something wrong?
    performance

    Difficulty 5/5 Over a week Newbie friendliness 35/100

    haskell/containers#1220 · 3 comments ·

  • Add tryInsert for sets and maps
    Open
    • Is something wrong?
    feature-request IntMap IntSet Map Set

    Difficulty 3/5 1-2 days Newbie friendliness 68/100

    haskell/containers#1205 · 7 comments ·

  • Next release, 0.8.1
    Open
    • Is something wrong?

    Difficulty 5/5 Over a week Newbie friendliness 25/100

    haskell/containers#1186 · 1 comment ·

  • Add unzip and unzipWith for Map and IntMap
    Open
    • Is something wrong?
    feature-request IntMap Map

    Difficulty 4/5 3-5 days Newbie friendliness 48/100

    haskell/containers#1174 · 8 comments ·

  • Set.split and Set.splitMember should be strict in the key
    Open
    • Is something wrong?
    major-release Set strictness

    Difficulty 3/5 1-2 days Newbie friendliness 45/100

    haskell/containers#1171 ·

  • `-> Solo a` functions for lazy maps
    Open
    • Is something wrong?
    feature-request IntMap Map

    Difficulty 5/5 Over a week Newbie friendliness 35/100

    haskell/containers#1132 · 2 comments ·

  • Strict maps as newtypes
    Open
    • Is something wrong?
    discussion/rfc IntMap Map

    Difficulty 5/5 Over a week Newbie friendliness 30/100

    haskell/containers#1124 · 13 comments · 3 reactions ·

  • Get tests working with MicroHs
    Open
    • Is something wrong?
    testing

    Difficulty 5/5 Over a week Newbie friendliness 25/100

    haskell/containers#1120 ·

  • Consider moving the tutorial off Read the Docs
    Open
    • Is something wrong?
    discussion/rfc docs

    Difficulty 5/5 Over a week Newbie friendliness 25/100

    haskell/containers#1100 ·

  • Improved representation for Set and Map
    Open
    • Is something wrong?
    discussion/rfc Map performance Set

    Difficulty 5/5 Over a week Newbie friendliness 20/100

    haskell/containers#1073 · 3 comments ·

  • Faster IntMap.size and IntSet.size
    Open
    • Is something wrong?
    IntMap IntSet performance

    Difficulty 4/5 3-5 days Newbie friendliness 35/100

    haskell/containers#1062 · 2 reactions ·

  • More efficient folds for Seq
    Open
    • Is something wrong?
    discussion/rfc performance Seq

    Difficulty 4/5 3-5 days Newbie friendliness 35/100

    haskell/containers#1036 · 6 comments ·

  • Add "Unsafe" modules
    Open
    • Is something wrong?
    discussion/rfc feature-request

    Difficulty 5/5 Over a week Newbie friendliness 25/100

    haskell/containers#1026 · 6 comments · 1 reaction ·

  • More accurate Set and Map size warnings
    Open
    • Is something wrong?
    docs Map Set

    Difficulty 2/5 1-3 hours Newbie friendliness 45/100

    haskell/containers#1010 · 3 comments ·

  • Full IntSets?
    Open
    • Is something wrong?
    discussion/rfc IntSet performance

    Difficulty 5/5 Over a week Newbie friendliness 25/100

    haskell/containers#999 · 5 comments ·

  • Errors when trying to generate a test coverage report
    Open
    • Is something wrong?
    testing

    Difficulty 4/5 3-5 days Newbie friendliness 25/100

    haskell/containers#997 · 10 comments ·

  • Data.Graph: detect cycles utility functions
    Open
    • Is something wrong?
    feature-request Graph

    Difficulty 5/5 Over a week Newbie friendliness 25/100

    haskell/containers#978 · 2 comments · 1 reaction ·

  • better instance Hashable IntSet?
    Open
    • Is something wrong?
    feature-request IntSet

    Difficulty 4/5 3-5 days Newbie friendliness 25/100

    haskell/containers#964 · 9 comments ·

  • Use generic map merging framework
    Open
    • Is something wrong?
    feature-request IntMap Map

    Difficulty 5/5 Over a week Newbie friendliness 28/100

    haskell/containers#937 · 6 comments · 1 reaction ·

  • Optimize scc as hard as possible
    Open
    • Is something wrong?
    Graph performance

    Difficulty 5/5 Over a week Newbie friendliness 20/100

    haskell/containers#929 · 3 comments ·

  • Should dfs be lazy?
    Open
    • Is something wrong?
    Graph performance

    Difficulty 5/5 Over a week Newbie friendliness 30/100

    haskell/containers#918 · 8 comments ·

  • Is graphFromEdges too lazy?
    Open
    • Is something wrong?
    Graph major-release performance

    Difficulty 5/5 Over a week Newbie friendliness 30/100

    haskell/containers#917 · 5 comments ·

  • Data.Graph.bcc is not efficient
    Open
    • Is something wrong?
    Graph performance

    Difficulty 3/5 1-2 days Newbie friendliness 42/100

    haskell/containers#900 · 7 comments ·

  • Data.Set.fromDistinctAscListN
    Open
    • Is something wrong?
    feature-request Set

    Difficulty 5/5 Over a week Newbie friendliness 25/100

    haskell/containers#894 · 9 comments ·

  • `haddock-autolink` submodule: Licensing, inclusion
    Open
    • Is something wrong?

    Difficulty 5/5 Over a week Newbie friendliness 18/100

    haskell/containers#891 · 6 comments ·

  • Improve powerSet performance
    Open
    • Is something wrong?
    performance Set

    Difficulty 5/5 Over a week Newbie friendliness 35/100

    haskell/containers#890 · 53 comments ·

  • Optimizing DFS in Data.Graph
    Open
    • Is something wrong?
    Graph performance

    Difficulty 5/5 Over a week Newbie friendliness 25/100

    haskell/containers#882 · 5 comments ·

  • Optimize mapping keys and values?
    Open
    • Is something wrong?
    feature-request Map

    Difficulty 5/5 Over a week Newbie friendliness 28/100

    haskell/containers#876 ·

  • Can we de-duplicate Set/Map by leveraging common structure?
    Open
    • Is something wrong?
    code-quality discussion/rfc

    Difficulty 5/5 Over a week Newbie friendliness 25/100

    haskell/containers#851 · 10 comments · 1 reaction ·

  • Data.Sequence time bounds: emphasize (stronger) that they are amortized?
    Open
    • Is something wrong?
    docs Seq

    Difficulty 2/5 1-3 hours Newbie friendliness 45/100

    haskell/containers#843 · 1 comment ·

  • Implement mapM for sequences
    Open
    • Is something wrong?
    performance Seq

    Difficulty 5/5 Over a week Newbie friendliness 25/100

    haskell/containers#838 ·

  • More `Map` functions could use pointer equality to avoid allocations in the no-op case
    Open
    • Is something wrong?
    Map performance

    Difficulty 4/5 3-5 days Newbie friendliness 38/100

    haskell/containers#836 · 1 comment ·

  • Why doesn't the `IntMap` and `IntSet` code use pointer equality checks to improve sharing and reduce allocations?
    Open
    • Is something wrong?
    IntMap IntSet performance

    Difficulty 4/5 3-5 days Newbie friendliness 48/100

    haskell/containers#835 · 1 comment ·

  • Flag adjustments for GHC-9.4 and tag inference.
    Open
    • Is something wrong?
    performance

    Difficulty 3/5 1-2 days Newbie friendliness 35/100

    haskell/containers#827 · 2 comments · 2 reactions ·

  • Add traverseMonotonic, etc.
    Open
    • Is something wrong?
    feature-request Map Set

    Difficulty 3/5 1-2 days Newbie friendliness 35/100

    haskell/containers#816 · 3 comments ·

  • Unboxed sums for performance (Discussion)
    Open
    • Is something wrong?
    discussion/rfc performance

    Difficulty 5/5 Over a week Newbie friendliness 20/100

    haskell/containers#801 · 1 comment · 3 reactions ·

  • Data.Sequence sort functions should be able to inline to eliminate unknown calls.
    Open
    • Is something wrong?
    performance Seq

    Difficulty 5/5 Over a week Newbie friendliness 32/100

    haskell/containers#799 · 2 comments ·

  • Add `spanAntitoneM`
    Open
    • Is something wrong?
    feature-request IntMap Map

    Difficulty 5/5 Over a week Newbie friendliness 28/100

    haskell/containers#798 · 4 comments ·

  • Add foldlWithKeyM
    Open
    • Is something wrong?
    feature-request IntMap Map

    Difficulty 3/5 1-2 days Newbie friendliness 38/100

    haskell/containers#793 · 4 comments ·

  • Feature request: Set.traverse
    Open
    • Is something wrong?
    feature-request Set

    Difficulty 5/5 Over a week Newbie friendliness 35/100

    haskell/containers#779 · 11 comments · 3 reactions ·

  • Feature request: `traverseKeys` and `traverseKeysWith`
    Open
    • Is something wrong?
    feature-request IntMap Map

    Difficulty 4/5 3-5 days Newbie friendliness 35/100

    haskell/containers#771 · 6 comments ·

  • Look into ways of writing an efficient `divvy`.
    Open
    • Is something wrong?
    Seq

    Difficulty 5/5 Over a week Newbie friendliness 35/100

    haskell/containers#770 · 2 comments · 1 reaction ·

  • Feature request: add traverseMaybe to IntMap
    Open
    • Is something wrong?
    feature-request IntMap

    Difficulty 3/5 1-2 days Newbie friendliness 45/100

    haskell/containers#754 · 1 comment ·

  • Add a Data.Sequence.Strict
    Open
    • Is something wrong?
    feature-request Seq

    Difficulty 5/5 Over a week Newbie friendliness 25/100

    haskell/containers#752 · 23 comments ·

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