Haskell/Getting set up

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This chapter will explore how to install the programs you'll need to start coding in Haskell.

[edit] Installing Haskell

First of all, you need a Haskell compiler. A compiler is a program that takes your code and spits out an executable which you can run on your machine.

There are several Haskell compilers available freely, the most popular and fully featured of them all being the Glasgow Haskell Compiler or GHC for short. The GHC was originally written at the University of Glasgow. GHC is available for most platforms:

• For MS Windows, see the GHC download page for details
• For MacOS X, Linux or other platforms, you are most likely better off using one of the pre-packaged versions for your distribution or operating system.

Note A quick note to those people who prefer to compile from source: This might be a bad idea with GHC, especially if it's the first time you install it. GHC is itself mostly written in Haskell, so trying to bootstrap it by hand from source is very tricky. Besides, the build takes a very long time and consumes a lot of disk space. If you are sure that you want to build GHC from the source, see Building and Porting GHC at the GHC homepage.

[edit] Getting interactive

If you've just installed GHC, then you'll have also installed a sideline program called GHCi. The 'i' stands for 'interactive', and you can see this if you start it up. Open a shell (or click Start, then Run, then type 'cmd' and hit Enter if you're on Windows) and type ghci, then press Enter.

You should get output that looks something like the following:

   ___         ___ _
  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 6.6, for Haskell 98.
/ /_\\/ __  / /___| |      http://www.haskell.org/ghc/
\____/\/ /_/\____/|_|      Type :? for help.

Loading package base ... linking ... done.
Prelude>

The first bit is GHCi's logo. It then informs you it's loading the base package, so you'll have access to most of the built-in functions and modules that come with GHC. Finally, the Prelude> bit is known as the prompt. This is where you enter commands, and GHCi will respond with what they evaluate to.

Let's try some basic arithmetic:

Prelude> 2 + 2
4
Prelude> 5 * 4 + 3
23
Prelude> 2 ^ 5
32

The operators are similar to what they are in other languages: + is addition, * is multiplication, and ^ is exponentiation (raising to the power of).

GHCi is a very powerful development environment. As we progress through the course, we'll learn how we can load source files into GHCi, and evaluate different bits of them.

The next chapter will introduce some of the basic concepts of Haskell. Let's dive into that and have a look at our first Haskell functions.