Haskell Mode for Emacs

This is the Haskell mode package for Emacs. Its use should be mostly self-explanatory if you're accustomed to Emacs.

When Emacs is started up, it normally runs a file called ~/.emacs (or ~/.emacs.d/init.el), ~ standing for your home directory. This file should contain all of your personal customisations written as a series of Emacs Lisp commands. In order to install the Haskell mode, you have to tell Emacs where to find it. This is done by adding some commands to the init file.

Installation

There are many ways to install haskell-mode. Pick the one that you're most comfortable with.

package.el

package.el is the built-in package manager in Emacs 24.x. On Emacs 23 you will need to get package.el yourself if you wish to use it.

haskell-mode is available on both Marmalade and MELPA community maintained repos.

If you're not already using Marmalade, add this to your ~/.emacs.d/init.el and load it with M-x eval-buffer.

(require 'package)
(add-to-list 'package-archives
             '("marmalade" . "http://marmalade-repo.org/packages/"))
(package-initialize)

For MELPA the code you need to add is:

(require 'package)
(add-to-list 'package-archives
             '("melpa" . "http://melpa.milkbox.net/packages/") t)
(package-initialize)

And then you can install:

M-x package-install [RET] haskell-mode [RET]

or

(when (not (package-installed-p 'haskell-mode))
  (package-install 'haskell-mode))

If the installation doesn't work right away try refreshing the package list first:

M-x package-refresh-contents [RET]

el-get

el-get is another popular package manager for Emacs. If you're an el-get user just do M-x el-get-install to get haskell-mode installed.

XEmacs

If you are using XEmacs, the haskell-mode package may be available for installation through the XEmacs package UI.

Emacs Prelude

haskell-mode is bundled with Emacs Prelude. If you're a Prelude user you can start using it right away.

Debian

If you are using Debian, you may be able to install the package haskell-mode with a command like:

$ apt-get install haskell-mode

Manual

• Download and unpack the basic mode and modules into a suitable directory, e.g. ~/lib/emacs/haskell-mode/ where ~ stands for your home directory.

• If you are using Emacs 21, you need an additional library, "syntax", from a later version of Emacs. The one you can get as http://cvs.savannah.gnu.org/viewcvs/*checkout*/emacs/emacs/lisp/emacs-lisp/syntax.el?rev=1.16 definitely works.

• Assuming you have placed the basic mode haskell-mode.el and the modules you want to use in the directory /lib/emacs/haskell-mode/, add the following command to your init file (/.emacs):

  (load "~/lib/emacs/haskell-mode/haskell-site-file")

  This only loads the bare-bones haskell-mode. To make it useful, you need additional modules; you can use the haskell customize-group to edit the Haskell mode hook or, if you prefer manual setup, try adding the following lines according to which modules you want to use:

  (add-hook 'haskell-mode-hook 'turn-on-haskell-doc-mode)
  (add-hook 'haskell-mode-hook 'turn-on-haskell-indentation)
  ;;(add-hook 'haskell-mode-hook 'turn-on-haskell-indent)
  ;;(add-hook 'haskell-mode-hook 'turn-on-haskell-simple-indent)

  Note that the three indentation modules are mutually exclusive - add at most one. Note that the line of code for simple indentation is commented out (using a preceeding ;) in preference for the more advanced indentation module. Installation is now complete!

The other modules are automatically loaded when needed in the following way:

• Font locking: just turn it on via global-font-lock-mode or do (add-hook 'haskell-mode-hook 'font-lock-mode)

• Declaration scanning: just use M-x imenu or bind imenu to a key. E.g. (global-set-key [(control meta down-mouse-3)] 'imenu) or you can also add it to the menubar with (add-hook 'haskell-mode-hook 'imenu-add-menubar-index)

• Interaction with inferior Haskell interpreter: just hit C-c C-z or C-c C-l.

Setup

Normally, inf-haskell automatically finds ghci or hugs in your PATH, but if that's not the case (common under Windows), or if you need to specify your preference, just tell Emacs which executable to use with:

(setq haskell-program-name "/some/where/ghci.exe")

If you want to use different settings when you use Cygwin Emacs and NTEmacs, you can test the value of system-type:

(setq haskell-program-name
      (if (eq system-type 'cygwin)
          "/cygdrive/c/ghc/ghc-6.8.1/bin/ghcii.sh"
        "c:/ghc/ghc-6.8.1/bin/ghci.exe"))

Note that Cygwin binaries tend to interact poorly with NTEmacs, especially w.r.t signal-handling.

Setup for new interactive mode

A new mode for the REPL and GHCi sessions is called haskell-interactive-mode, it intends to replace inferior-haskell-mode, but comes with different features.

There are new modules for handling the following things:

• Separate sessions per Cabal project (haskell-session.el).
• A new inferior Haskell process handling code (haskell-process.el).
• New REPL (haskell-interactive-mode.el).
• Bunch of new features based upon the above three things.

To make use of them, try out the instructions in examples/init.el. WARNING: The features expressed in here are new and many are Linux-specific.

Note: These features are entirely orthogonal to the older inferior-haskell-mode, and therefore keybindings which work for inferior-haskell-mode will not magically work for the above new modules.

Customization

Most customizations are on the functionality of a particular module. See the documentation of that module for information on its customisation.

There is also a wiki page listing tips and tricks.

Known problems

It seems that some versions of XEmacs come without the fsf-compat package (which provides functions such as line-end-position) and it seems that even if your XEmacs does have the fsf-compat package installed it does not autoload its part. Thus you may have to install the fsf-compat package and add (require 'goto-addr) in your .emacs.

Multi-mode editing

For LaTeX-based literate Haskell, you might be interested in the multiple major mode package haskell-latex.el (plus multi-mode.el) from http://www.loveshack.ukfsn.org/emacs/.

Support

• Github homepage
• Mailing list

Contributing

For submitting pull requests, please see the wiki page on contributing. You don't have to follow this guide, but please make sure your pull requests are at least properly rebased and up to date.