2010-03-20
Haskell From Scratch - 1. Introduction
Hello. Yesterday I installed Haskell and today I tried to learn it. I am not much better off now as I was before I installed it, except now I can run Haskell things.
Why? Because the resource I'm using to learn it, although recommended to me, has the same problems as all the other resources you use to learn languages. That is, they give you all the building blocks with incoherent examples (incoherent between one another, not to say that each example makes no sense per se) from which you are somehow magically supposed to go "Ah yes, now I have what I need to write a program in Haskell!".
Believe it or not, it doesn't work. That is why I am going to do it the way all good software developers do anything, which is to dive right in without any sort of forward planning whatsoever.
The Game
The game will be a command-line game and it will be a throwback to the early days of computer gaming. First there was Adventure, then Zork, and Hitch-Hikers Guide to the Galaxy, and many besides.
Let's relive the glory days in modern style and run a Zork game in Haskell. I chose this sort of game for three reasons:
- It runs on the command line. This means we don't have to worry about things like graphics or processor speed or even compatibility. If you can run Haskell you can run the game.
- The game is simple. It's basically a call-and-response game. You type a thing, processing happens, and it says something. What it says is the meat of the program and hence point three.
- It is extensible. Whenever we think of an idea we can add it to the list of things to do when we get around to it. We can start off simple and finish off complex and all we need in order to create new things and new adventures is the sadly rare ability to speak English.
Haskell
SubStack suggested I not use the Debian (or Ubuntu) ports of ghc because as
valiant as the maintainers try to be they are always way behind on this sort
of thing. So I installed it from source. You can get the distribution
packages here.
Distro packages usually suck so you can get the source
here. Follow the
INSTALL file's instructions and you get the basic Haskell compiler,
whereupon you should get the newest version of cabal-install from
here You can simply run the bootstrap.sh that comes with that in
order to install cabal. It installs the executable to somewhere in your home
directory so you might want to put it somewhere like /usr/bin or somewhere
else in your $PATH.
Anyway, cabal is the package manager for Haskell, like cpan is to Perl. It will become useful.
To check it's working, run ghci. When I did this I got an error about gmp.
Unfortunately, when I got gmp from source and installed it, it still didn't
work, so I ran apt-get install libgmp3-dev. Naturally, this won't work on
non-Debian systems so head over to gmplib.org if your
package manager doesn't have it, and get it.
Remember that Haskell is still maturing as a lanaguage and as a whole suite of libraries and packages that support it, so stuff being a problem is likely to happen until a decent implementation of everything comes out of the miasma. Think about Perl, which is on 5.10 in the mainstream now, and it barely has a passable package manager!
Next in this series I'll have worked out how to actually start. Tune in!