UMBC CMSC331-01 Programming Languages, Fall 2024

Running Haskell Programs

ghc file1.hs file2.hs ... -o run.out

% ghc Main.hs Qsort.hs -o dothis.out
[1 of 2] Compiling Qsort            ( Qsort.hs, Qsort.o )
[2 of 2] Compiling Main             ( Main.hs, Main.o )
Linking dothis.out ...

% ./dothis.out
[1,2,3,5,7,9]

% ghci Qsort.hs
GHCi, version 9.0.2: https://www.haskell.org/ghc/  :? for help
[1 of 1] Compiling Qsort            ( Qsort.hs, interpreted )
Ok, one module loaded.
ghci> qsort [7,2,1,9]
[1,2,7,9]
ghci> :quit
Leaving GHCi.
%

Installing Haskell

On GL (default option)

On Windows 10 and 11

Steps:

1. First make sure that WSL is enabled on your Windows system. From the Start Menu, search for "Turn Windows features on or off". Click on the Control Panel result from that search. This brings up a window with a bunch of checkboxes. Scroll to the bottom and see if the box for "Windows Subsystem for Linux" is checked. If not, check that box, click "OK" and reboot your machine.

2. Go to the Microsoft Store and search for "WSL". Choose one of the Linux distributions available. Either "Ubuntu" or "Debian" is recommended.

3. After Debian or Ubuntu is installed, launch the app. This will bring up a terminal window. Allow the system to do some housekeeping after the first launch. This could take a few minutes. You will be asked to create a super-user account and password. Remember this password! You will need the password to install packages.

4. When the Linux distribution is ready, first update the packages:

      sudo apt update
      

5. Next, install GHC and the PCRE module

      sudo apt install ghc libghc-regex-pcre-dev
      

6. You will also want to install some Linux tools that might not be already installed, such as emacs, vim, openssh-client, rsync, ... These can be easily installed using the sudo apt install command.

sudo apt remove ghc 

Linux

If your Linux distribution does not have a package for Text.Regex.PCRE, you would have to install it using cabal, the native Haskell package manager. Check if cabal is already installed with ghc, if not it is likely in a separate package called cabal-install. After installing cabal:

cabal update
cabal v1-install regex-pcre

ghc-pkg list

cabal install --lib regex-pcre

Note: cabal takes about 1GB of storage in the .cabal directory in your home directory. When you are done with Haskell, you can safely trash .cabal.

On MacOS

MacOS is Unix underneath. So, you just need to install the GHC package. Since MaCOS does not come with its own package manager, you have to first install a package manager. The recommended package manager is Homebrew. If you already have another package manager installed (e.g., Macports or Fink), you can also install GHC using those package managers.

MacOS installation is complicated by three things:

1. The steps vary a bit depending on which shell you use. The Unix command to install Homebrew on their website works for sh, bash and zsh. If you are using csh or tcsh, you should fire up zsh (the default MacOS shell these days) to run the Homebrew installation command. Also, for csh and tcsh, each time you install something using Homebrew, you should issue a rehash command to make the new command available to you.
2. The steps vary a bit depending on which version of MacOS you have. The following has been tested on Ventura (MacOS 13.5), Monterey (MacOS 12.5) and Big Sur (MacOS 11.6). Mojave (MacOS 10.14) is not supported by Homebrew. I have not checked Catalina (MacOS 10.15).
3. Neither Homebrew nor MacPorts has the PCRE package for Haskell as a library install. We have to use cabal, the native Haskell package manager to get the Text.Regex.PCRE module. OTOH, Fink appears to have a PCRE package, but I have not tested this. If you are running Fink, try installing it and check if you have the Haskell PCRE module (see below.)

1. Go to the Homebrew web page and copy the Unix command under the heading "Install Homebrew". The command starts with

      /bin/bash -c "$(curl -fsSL ...
      

2. Launch the MacOS Terminal app. (Drop into zsh if you are using csh or tcsh.) Paste the command at the Unix prompt. Wait for Homebrew to finish installing.

3. After Homebrew is done with its installation, check if the brew command is available. If not, follow the instructions to add the path to the commands installed by Homebrew to your PATH environment variable.

   The actual path might vary depending on versions. It might be /opt/homebrew/bin or /usr/local/bin.

   If you are using csh or tcsh, manually add the path in your .cshrc or .tcshrc file instead of using the instructions provided by the Homebrew installer.

   Logout and log back in and check if the brew command is available.

4. Next, you can use Homebrew to install GHC:

      brew install ghc
      

In addition to ghc, you need to install the PCRE module (Perl Compatible Regular Expressions) for Haskell. This is somewhat more complicated on MacOS since Homebrew does not supply the binaries and we need to use cabal to download and install the package. This means we need to install cabal and some system tools:

brew install cabal-install
brew install pkg-config
brew install pcre

Depending on which shell you use, you may need to issue the rehash command to see the newly installed utilities. Then, we can use cabal to install Text.Regex.PCRE:

cabal update
cabal v1-install regex-pcre

import Text.Regex.PCRE

Note: cabal takes about 1GB of storage in the .cabal directory in your home directory. When you are done with Haskell, you can safely trash ~/.cabal.

On Android (not recommended)

1. First, on your Android device, go to the F-Droid site and download the F-Droid .apk file. Then, using your favorite Android file manager, install the .apk file. You may need to change your system settings to allow your file manager to install apps. (You can change it back after installing F-Droid.)

2. Run the F-Droid app. Go to the updates panel. Update F-Droid itself, if available. You may need to change your system settings to allow F-Droid to install and update apps.

3. In the F-Droid app, search for "Termux". Install the Termux app.

4. Launch Termux. There are some housekeeping commands you need to issue:
   • First, update Termux itself

     pkg update
     

   • Second, allow Termux to access the Android file system

     termux-setup-storage      
     

     Your Android files are linked under storage or you can go directly to /sdcard.
   • Next, install any Linux utilities that you like using the pkg install command. Termux has many but not all Linux packages in its repository.

5. Now you can install ghc and cabal in Termux:

   pkg install ghc
   pkg install cabal-install
   

6. You can optionally install dnsutils. If you don't, cabal will complain that it can't run nslookup, but will carry on and work anyway:

   pkg install dnsutils
   

7. Next, we initialize cabal and install the PCRE module:

   cabal update
   cabal v1-install regex-pcre
   

8. Finally, check whether the library was installed correctly:

   ghc-pkg list
   

   You should see some version of regex-pcre in the list. You can also check if the Text.Regex.PCRE package was installed correctly by running ghci and typing:

   import Text.Regex.PCRE
   

Note: cabal takes about 1GB of storage in the .cabal directory in your Termux home directory. When you are done with Haskell, you can safely trash ~/.cabal.