If you’re the horrible sort of person who doesn’t read introductions, you might want to go back and read the last section anyway—it explains how to use this book, as well as how to load functions with GHC.
First, let’s start GHC’s interactive mode and call some functions, so we can get a very basic feel for Haskell. Open a terminal and type
ghci. You will be greeted with something like this:
GHCi, version 6.12.3: http://www.haskell.org/ghc/ :? for help Loading package ghc-prim ... linking ... done. Loading package integer-gmp ... linking ... done. Loading package base ... linking ... done. Loading package ffi-1.0 ... linking ... done.
GHCi’s default prompt is
Prelude>, but we’ll be using
ghci> as our prompt for the examples ...