Technical requirements

Up to now, we have only used modules from Haskell’s standard library. In this chapter, we will briefly touch upon two additional libraries that have to be installed separately, called random and time. Such libraries, which provide a number of modules, are called packages.

You can use the cabal build tool for Haskell to install packages where the ghc compiler can find them. Cabal draws its packages from Hackage, which is a large repository of publicly available Haskell packages. You can browse Hackage at https://hackage.haskell.org/.

To install the two relevant packages, you need to run the following two commands:

$ cabal install random
$ cabal install time

These will download and compile the two packages, and then make sure the ghc compiler can find them for use in the programs you write. For example, after the installation of the random package, we can simply access its System.Random module in our program by writing an import declaration at...