A pragmatic guide to monad transformers
When to reach for mtl, when to use plain ReaderT, and how to keep error stacks legible across a real codebase.
02 — Resources
A working library
Hand-picked articles, videos, libraries, and tools. Filter by pillar to narrow the list.
servant 0.21 in production
A field report from a team running servant-based services for three years. Patterns that scaled, ones that did not.
Discourse thread: hiring junior Haskellers
Practitioners share what worked when bringing developers without prior Haskell experience onto production teams.
Type families, slowly — a recorded workshop
Three hours, paced for working developers. Builds intuition for closed and open type families through a worked example.
A starter Nix flake for Haskell projects
Minimal flake.nix you can copy in: GHC 9.10, HLS, fourmolu, and a dev shell that just works.
Lazy evaluation, debugged
Reading :sprint, spotting accidental thunks, and a shortlist of strictness annotations that pay rent.
ZuriHac 2026 — June 12–14
The annual gathering returns to Rapperswil. Hack on libraries, meet maintainers, eat lake-side lunches.
persistent + esqueleto cookbook
Recipes for the queries you actually write: joins, conditional updates, batched inserts, soft deletes.
“Haskell at Work” — second edition
A practical book of complete projects: a CLI, a web service, a streaming pipeline. Updated for GHC 9.10 idioms.
#haskell-beginners on Matrix
A patient room for first questions. Answered, on average, within fifteen minutes during European working hours.
Records, finally: OverloadedRecordDot in practice
A migration log: how we moved a 60k-line code base off lens-based field access without breaking compile times.
A field guide to Foldable
The instances, the laws, and the small-ish lookup table you can keep on your desk to read code faster.
No resources match this filter.
Essential Toolkit
04 — Toolkit
What we keep on the bench
The tools most working Haskellers reach for. Versions are kept current with stable releases.
GHC
9.10.1The Glasgow Haskell Compiler. The canonical implementation; what production code is built with.
cabal-install
3.12.1Project building and dependency resolution. Pairs with Hackage; speaks `.cabal` files.
Stack
2.15.7Curated snapshots through Stackage. Reproducible builds without a flake or pin file.
HLS
2.9.0Haskell Language Server. Editor integration, type-on-hover, code actions, formatting hooks.
GHCup
0.1.30Installer and toolchain manager. The friendliest way to keep multiple GHCs side-by-side.
fourmolu
0.16.2Configurable code formatter. The community default for projects that want predictable diffs.
hlint
3.8Suggestions for cleaner Haskell. Enforceable in CI, configurable per project.
cabal-fmt
0.1.10A formatter for `.cabal` files. Keeps stanza ordering and comment placement consistent.
Community Board
05 — Community
Where Haskellers gather
Highlights from people building things, plus the channels where conversation actually happens.
Community Highlights
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A pragmatic guide to monad transformers
“Most of the time you do not need
mtl. Most of the time you do, you only need three layers.” -
servant 0.21 in production
A field report on running servant-based services for three years — what scaled and what we replaced.
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Showcase:
polyglot-rpc1.0A typed RPC layer that speaks JSON, MessagePack, and Protobuf. Schema lives in Haskell, clients in seven languages.
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Discussion: junior hiring, what worked
A long thread of stories from teams that brought in juniors without prior Haskell experience and made it work.
Contribute
Help keep this workshop tidy
haskeller.net is community-maintained. Suggest a resource, fix a broken link, or submit a write-up — everything happens in a single repo with light review and short feedback loops.