by Carsten König

Getting started with using SublimeHaskell and Cabal

I recently started using Sublime Text 2 as my main editor for non .net related languages – and I really enjoy it (I think I will pay Mr. Skinner soon – well deserved!).

If you are working with Haskell, then there is a rather good plugin named SublimeHaskell you can use to get automatic compile-error reporting (on save) and an integrated type query and type insert mechanism I quite like.

But in order to get this you have to set up your Haskell project with cabal and install the plugin first.

Install the SublimeHaskell-plugin

The installation itself is very simple once you installed the “Package Control” for Sublime Text 2 (see the link – it’s basically nothing more than running the following snippet inside the Sublime Text 2 console).

import urllib2,os;
pf='Package Control.sublime-package'; 
ipp=sublime.installed_packages_path(); 
os.makedirs(ipp) if not os.path.exists(ipp) else None; 
urllib2.install_opener(urllib2.build_opener(urllib2.ProxyHandler())); 
open(os.path.join(ipp,pf),'wb').write(urllib2.urlopen('http://sublime.wbond.net/'+pf.replace(' ','%20')).read()); 
print 'Please restart Sublime Text to finish installation'

With the Package Control ready you just have to use the package-install, search for SublimeHaskell and hit return – done.

Setup a basic Haskell Cabal project

Create a folder for your project and create your Haskell source file(s) – here I’m using a very basic one:

-- Greetings.hs
-- Copyright (c) 2012 Carsten König 
-- 

module Greetings where 
import System.Environment

main :: IO ()
main = getArgs >>= print . greetings . head   

greetings s = "Hello! " ++ s

Next create a .cabal file for your project – this is where you tell Cabal how to build/install your files and what dependencies it has, etc.(see the Cabal user guide for additional information):

Name:                greetings 
Version:             0.0 
Description:         say Hi 
License:             GPL 
Author:              Carsten König 
Maintainer:          Carsten@gettingsharper.de 
Build-Type:          Simple 
Cabal-Version:       >=1.2  

Executable greetings
   Main-is:           greetings.hs
   Build-Depends:     base >= 3 && < 5 
&#91;/sourcecode&#93;
</pre>
</div>
<p>Important are the name (which names your package), Executable &lt;name&gt; (the –o(utput) name) and Main-is entry.</p>
<p>Finally you will need a (very basic) Setup.hs script for cabal:</p>
<div style="padding-bottom: 0px; margin: 0px; padding-left: 0px; padding-right: 0px; display: inline; float: none; padding-top: 0px" id="scid:C89E2BDB-ADD3-4f7a-9810-1B7EACF446C1:d554d603-bad7-4199-8f61-e66344473225" class="wlWriterEditableSmartContent"><pre style=white-space:normal>

import Distribution.Simple 
main = defaultMain

That’s it – now you can install/build your project with Cabal like this:

cabal install --prefix=$HOME--user

Please note: $HOME is where cabal should write your binary output to – it will create/use a “bin”-folder right below $HOME.

That’s it – now whenever you save your file in SublimeText it ghc will run it and possible errors will show like this:

SublimeBuildFailed

And even better: if you mapped your keybindings in the “Preferences/Key Bindings – User” settings of Sublime Text like this:

    {
        "command": "haskell_show_type",
        "context": "source.haskell",
        "keys": ["ctrl+k", "ctrl+h", "ctrl+t"]
    },
    {
        "command": "haskell_insert_type",
        "context": "source.haskell",
        "keys": ["ctrl+k", "ctrl+h", "ctrl+i"]
    }

You can put the cursor on a method, use the sequence <Ctrl>-<K>, <Ctrl>-<H>, <Ctrl>-<T> to see the type of the expression:

SublimeTypeInterference

Or hit <Ctrl>-<K>, <Ctrl>-<H>, <Ctrl>-<I> to add the type above your method:

SublimeType

Neat isn’t it Smiley mit geöffnetem Mund (aside from not noticing String = [Char])