Thursday, May 13, 2010

Installing GHC 6.12.2 on Red Hat Entrprise Linux 5.4 (i386)

Haskell, a general-purpose, purely functional programming language, has become more and more interesting for me, it allows me to write maintainable code, with acceptable performance even for tasks like analyzing large log files. I recently discovered how easy it is to write programs interacting with a unix like environment. It also very easy to write networking code. Haskell offers great opportunities for TDD and SDD through HUnit and QuickCheck, which - together with the pure and strong static type system of the language itself - enable trust in program correctness, which is vital for many commercial applications, or applications exposed to increased security requirements.

In order to leverage the outstandingly great features of Haskell, one has to have that beast running on a stable, proven and hence archaic and outdated operating system. Even if one is not a firm believer in magical awesomeness of Enterprise labels on top of ridiculously obsolete tools(like gcc 4.1 and glibc 2.5), the server landscape might require to use a specific Linux distribution, because of proprietary drivers for specialized hardware components, in this post I will assume that this Linux distro is Red Hat Entrprise Linux 5.4 and explain the cumbersome installation of the latest and greatest Haskell compiler.

Step 0: Preparing the build environment

As a non-commercial 100% binary compatible replacement for RHEL with only the proprietary art work replaced Cent OS should be used. I installed Cent OS 5.4 i386 without any GNOME or KDE and with bridge networking in a Virtual Box with on an Arch Linux host.

Step 1: Installing GHC 6.8.3

Because the generic binary linux distribution of GHC 6.12.2 depends on at least the 2.7 version of glibc, and RHEL 5.4 only provides glibc 2.5, it is necessary to build it from the sources. Strangely the GHC source distribution needs an existing GHC to compile it: in order to compile GHC 6.12.2 from source we need to have a GHC already installed. The latest GHC version with a generic linux binray distribution compatible with glibc 2.5 is GHC 6.8.3.

These are the required commands(execute as root) to install GHC 6.8.3 into /usr/local:

[root@noname ~]# wget
[root@noname ~]# tar xvfj ghc-6.8.3-i386-unknown-linux.tar.bz2
[root@noname ~]# cd ghc-6.8.3
[root@noname ghc-6.8.3]# ./configure
[root@noname ghc-6.8.3]# make install

Try running ghci, the interactive Haskell REPL, it should start and welcome its user with a warm...

[root@noname ~]# ghci
GHCi, version 6.8.3: :? for help
Loading package base ... linking ... done.

Step 2: Building GHC-6.12.2

GHC 6.12.2 can now be built from source using the GHC 6.8.3 from the previous build...

tar xfvj ghc-6.12.2-src.tar.bz2
cd ghc-6.12.2

STOP do not make install just yet. Before, move your /usr/local/ to /usr/local.ghc683 in order to get a clean
install of GHC 6.12 in /usr/local with make install.

Harvest the result of your hard work

Now would be an excellent moment to save a snapshot of your /usr/local directory.
If I knew where I would even upload an archived version of mine.

Sunday, May 09, 2010

haskell stuff in my .emacs

This does not include the ghc-mod configuration.

;; haskell section:
(load "/usr/share/emacs/site-lisp/haskell-mode/haskell-site-file.el")
(require 'inf-haskell)
(autoload 'turn-on-haskell-doc-mode "haskell-doc" nil t)
(add-hook 'haskell-mode-hook 'heyllStd)
(add-hook 'haskell-mode-hook 'turn-on-haskell-font-lock)
(add-hook 'haskell-mode-hook 'turn-on-haskell-decl-scan)
(add-hook 'haskell-mode-hook 'turn-on-haskell-indent)
(add-hook 'haskell-mode-hook 'turn-on-haskell-doc-mode)
(add-hook 'haskell-mode-hook 'turn-on-haskell-ghci)