IDE library for Haskell based on the GHC API. This is not a real fork. I will upload my patches here so that nominolo can pick them
Haskell Emacs Lisp
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Scion is a Haskell library that aims to provide Haskell source code inspection and transformation functionality as well as various other features that may be useful for an IDE.

Most of Scion's functionality is based on the GHC API. Scion tries to be front-end agnostic; it provides both a Haskell API and servers for non-Haskell clients such as Emacs (no Vim, volunteers required).


(For developer builds see section "Hacking" below.)

Scion requires GHC 6.10.1 or later. All other dependencies should be on Hackage and can be installed using cabal-install:

$ cd dir/to/scion
$ cabal install

Scion supports various configuration flags which are useful when working on Scion itself.





$ cd <scion>
$ cabal install -femacs
$ ./.cabal/bin/emacs_server


(add-to-list 'load-path "<scion>/emacs")
(require 'scion)

(add-hook 'haskell-mode-hook 'my-scion-hook)
(defun my-scion-hook ()
  (scion-mode 1))

M-x scion-connect
M-x scion-open-cabal-project
M-x scion-load-library

C-c i l  -- insert language pragma
C-c i p  -- insert pragma
C-c i m  -- insert (external) module name

Bug Reports

Please send bug reports or feature requests to the Issue tracker.


For discussions about Scion use the scion-lib-devel mailing list.


The main repository for Scion is hosted on Github. Get it via

$ git clone git://

Send patches or pull requests to nominolo (email address at googlemail dot com). Note that, if you fork the project on Github your fork won't take up additional space on your account.


For development it is probably easier to use the GNU make than Cabal directly. The makefile includes a file called which is not present by default. You can use the provided and edit it:

$ cp
$ edit

After that, the makefile takes care of the rest.

$ make           # configure and build
$ make install   # configure, build, and install

If you don't have the dependencies, yet, and have cabal-install, the following may be helpful (If it's not in the path, adjust accordingly):

$ make cabal-install

(This also installs Scion, but that shouldn't interfere with hacking.)

Using an in-place GHC

GHC 6.10.1 has a couple of problems. For example, not all error messages are reported using the GHC API but instead are printed to stdout/stderr. Some parts also call exitWith directly. GHC's HEAD branch has some of these bugs fixed and may contain new features not present in the stable branch. If you want to compile against an inplace GHC, the following steps should work:

  1. On windows, make sure that Cabal finds the inplace gcc

    $ cd /path/to/ghc
    $ cp `which gcc` ghc/

    (Adjust to version of GCC that GHC was compiled with.)

  2. Set the GHC_PATH variable to the correct path to for your system. Make sure not to set HC, PKG, or HADDOCK, they will automatically be set to point to the inplace versions.

  3. Use make or make cabal-install as above.