**Course Title:** Functional Programming with Haskell: From Fundamentals to Advanced Concepts **Section Title:** Haskell Deployment and Ecosystem **Topic:** Packaging and Distributing Haskell Applications **Introduction:** As a Haskell developer, you have learned how to write functional and maintainable code. However, deploying your application to various platforms can be challenging. In this topic, we will explore how to package and distribute Haskell applications, making them available to users on different operating systems. **What is Cabal?** Cabal (Common Architecture for Building Applications and Libraries) is a package management system for Haskell. It helps you manage dependencies, build, and distribute Haskell projects. Cabal provides a way to create self-contained packages that can be easily installed and shared with others. **Creating a Cabal Project:** To create a Cabal project, you can use the `cabal init` command. This will ask you a series of questions to generate a basic `.cabal` file for your project. ```bash $ cabal init ``` **Understanding the .cabal File:** The `.cabal` file is the central configuration file for your project. It contains metadata about your project, such as its name, version, and dependencies. ```haskell -- Name of your package name: my-haskell-app -- Version number version: 1.0.0 -- Dependencies build-depends: base >= 4.10 && < 5 ``` **Building and Installing with Cabal:** Once you have created your `.cabal` file, you can build and install your project using Cabal. ```bash $ cabal build $ cabal install ``` **What is Stack?** Stack is a modern build tool for Haskell. It uses Cabal under the hood but provides a more streamlined experience for building and deploying Haskell applications. Stack also includes tools for managing dependencies and building executables. **Using Stack to Package and Distribute Haskell Applications:** Stack provides a simple way to create and distribute Haskell applications. To get started, you can create a new Stack project using the `stack new` command. ```bash $ stack new my-haskell-app ``` **Creating a Stack YAML File:** The `stack.yaml` file is used to configure the Stack project. It contains metadata about your project, such as its name, version, and dependencies. ```yml -- Name of your package name: my-haskell-app -- Version number version: 1.0.0 -- Dependencies dependencies: - base ``` **Building and Installing with Stack:** Once you have created your `stack.yaml` file, you can build and install your project using Stack. ```bash $ stack build $ stack install ``` **Creating and Distributing Executables:** Both Cabal and Stack provide a way to create executables for your Haskell application. These executables can be distributed and run on various platforms. ```bash -- Create an executable with Cabal $ cabal build $ cabal run -- Create an executable with Stack $ stack build $ stack run ``` **Best Practices for Packaging and Distributing Haskell Applications:** 1. Use a consistent naming scheme for your packages and executables. 2. Keep your dependencies up to date to ensure compatibility. 3. Use `cabal freeze` or `stack freeze` to lock your dependencies. 4. Provide clear and concise documentation for your package. 5. Use testing frameworks like HUnit and QuickCheck to ensure your code is reliable. **Conclusion:** In this topic, we explored how to package and distribute Haskell applications using Cabal and Stack. By following best practices and using these tools, you can create and share maintainable Haskell projects with others. **What's Next?** In the next topic, we will cover "Creating Executables with Stack and Cabal." **External Links:** * [Cabal Documentation](https://cabal.readthedocs.io/en/latest/) * [Stack Documentation](https://docs.haskellstack.org/en/stable/) * [Haskell Wiki: Packaging and Distribution](https://wiki.haskell.org/Packaging_and_distribution) **Leave a Comment or Ask for Help:** Please feel free to ask for help or leave a comment if you have any questions or need further clarification on any of the topics covered.

$ cabal init

-- Name of your package
name: my-haskell-app

-- Version number
version: 1.0.0

-- Dependencies
build-depends:
  base >= 4.10 && < 5

$ cabal build
$ cabal install

$ stack new my-haskell-app

-- Name of your package
name: my-haskell-app

-- Version number
version: 1.0.0

-- Dependencies
dependencies:
  - base

$ stack build
$ stack install

-- Create an executable with Cabal
$ cabal build
$ cabal run

-- Create an executable with Stack
$ stack build
$ stack run