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Haskell practicalities

Getting started with Haskell programming covered the recommended way to get going with Haskell: installing GHC, cabal and the Haskell Language Server using GHCup, and then obtaining the code for this book from either Hackage or GitHub. This appendix1 covers the alternatives: other ways to install Haskell locally, and – often more useful for a reader who just wants to try something out first – several ways of running Haskell without installing anything at all.

Installing Haskell locally

GHCup, https://www.haskell.org/ghcup/, described in Getting started with Haskell programming, is the toolchain installer that haskell.org itself recommends, and remains the best starting point on Linux, macOS and Windows (native or under WSL). A system package manager – Homebrew’s ghc and cabal-install on macOS, apt on Debian/Ubuntu, Chocolatey on Windows – can also install a Haskell toolchain, but the versions provided are often out of date, so GHCup remains the better default. Readers who prefer the Stack build tool to Cabal can instead run stack setup, which fetches and manages its own GHC.

Readers who would rather not install anything directly onto their own machine, but who already have Docker installed for other reasons, can use the official Haskell Docker image instead:

docker run -it haskell:9.6 ghci

This gives a disposable GHC, cabal and Stack installation inside a container, with no risk of it clashing with anything else already on the machine.

Running Haskell with nothing installed

For a reader who wants to try the book’s actual code – including its multi-module structure and dependencies such as QuickCheck – without installing anything, the best option is a cloud development environment. This book’s GitHub repository includes a dev container configuration which builds a ready-to-use GHC, cabal and HLS environment with the code for the book already built. It can be used in a couple of ways:

  • GitHub Codespaces: on the repository’s GitHub page, https://github.com/simonjohnthompson/haskellcraft, click Code, then the Codespaces tab, then Create codespace on main. This opens a full, browser-based copy of VS Code, already connected to a virtual machine with Haskell installed; GitHub gives every personal account a free monthly quota of Codespaces hours.

  • With Docker and VS Code’s Dev Containers extension installed locally, opening a clone of the repository and choosing Reopen in Container uses the same configuration, without needing a cloud service at all.

In each case, once the container has finished building – the first time takes a few minutes, so watch for the “Running postCreateCommand” notification to complete – opening a terminal and typing cabal repl gives a working ghci prompt with all of the book’s code and dependencies available, exactly as described in Working with multiple-module projects; opening a .hs file gives the usual IDE features through HLS.

For trying out a single short expression or function, rather than the book’s code as a whole, an online playground may be quicker still. The current, officially maintained one is https://play.haskell.org; it compiles a single file containing a main function and produces a shareable link, but does not support GHCi-style interaction or the book’s package dependencies. (An older, once widely-recommended site, tryhaskell.org, closed in 2025 after sixteen years of service; if you see it mentioned elsewhere, use play.haskell.org instead.) A number of general-purpose online IDEs – Replit, JDoodle, OneCompiler and others – also support Haskell to varying degrees, and may be convenient if you already use one of these for other purposes, though none is Haskell-specific.

Two further approaches are worth knowing about, though neither is yet a good fit for this book. Since version 9.6, GHC has had an experimental WebAssembly backend, and a public demonstration, https://haskell-wasm.github.io/ghc-in-browser/, runs GHC itself inside the browser tab with no server involved at all; today, though, it supports no external packages and so cannot build the book’s code. Jupyter notebooks can also be used for Haskell via the IHaskell kernel, and a repository can be made launchable with no installation using https://mybinder.org; this gives a capable, genuine environment, but with a much slower start-up than the dev container described above, so it isn’t needed here.

Getting the Craft3e code

Working with multiple-module projects describes in detail how to obtain and build the code for this book, either from Hackage using cabal unpack Craft3e, or by cloning the book’s GitHub repository, https://github.com/simonjohnthompson/haskellcraft.

Using GHCi

An overview of the main commands of GHCi can be found in Principal GHCi commands, and full details of other aspects of GHCi are in the online documentation for GHC.

Editors and IDEs for Haskell

As discussed in Getting started with Haskell programming, Visual Studio Code together with the Haskell Language Server (HLS) is a good default choice: it is free, cross-platform, and provides type checking, refactoring and other IDE features once the haskell.haskell extension is installed. Several other editors have long-standing Haskell support, and remain popular with readers who prefer a terminal-based workflow: emacs, via its Haskell mode, https://github.com/haskell/haskell-mode; and vim, via https://github.com/neovimhaskell/haskell-vim. An overview of editor support more generally can be found at https://wiki.haskell.org/Editors.

  1. This appendix was drafted with assistance from Claude Code v2.1.236 (Claude Sonnet 5), Anthropic, 2026. ↩