Why

Emacs is an excellent editor for Haskell, but it requires a lot of configuration to get haskell-mode and ghc-mod installed and working. Especially tricky is that the tools you need to set up a decent .emacs.d environment aren't blessed or highlighted anywhere.

This init.el chooses Sane Defaults™ (use-package and Cask) to help get you started, and comments are sprinkled liberally in case you want to tweak it.

Installing

Before you get started, you'll need (as of writing) cabal-helper in your global stack.yaml, because it doesn't (yet) have a Stackage entry. Open up ~/.stack/global/stack.yaml in your favorite text editor and make sure it looks like this.

flags: {}
packages: []
extra-deps:
  - cabal-helper-0.6.0.0
resolver: lts-3.20

Go to the Stackage website and use the latest resolver. It almost definitely won't be 3.20 by the time you read this.

When that's done, you'll be ready to clone and run the handy-dandy setup script I wrote.

git clone https://github.com/hlian/emacs-scratchpad-haskell ~/.emacs.d
cd !$
./RUNME.sh

Features

• Syntax highlighting (haskell-mode)
• Syntax checking (ghc-mod or hlint)
• All the other fantastical ghc-mod features
• Supports GHC 7.10 and Stack, in addition to older GHCs and Cabal
• Package management with Cask
• No impact on Emacs startup performance (use-package)

Try this

• cd /tmp/scratch
• stack new
• stack build -- an unfortunate bug means you need to build before opening (as of writing)
• emacs app/Main.hs
• Move cursor to IO
• Hit Ctrl-c, Ctrl-i to do the equivalent of an :info
• Hit Ctrl-c, Ctrl-l to load the code into a GHCi session
• Hit Ctrl-x, o to move to the session buffer
• Type :info IO and hit Enter