**Course Title:** Functional Programming with Haskell: From Fundamentals to Advanced Concepts **Section Title:** Introduction to Functional Programming and Haskell **Topic:** Install Haskell, write and run a simple Haskell program to understand basic syntax.(Lab topic) **Objective:** By the end of this lab, you will have a working Haskell environment, understand the basic syntax of Haskell, and be able to write and run a simple Haskell program. **Prerequisites:** Please ensure you have completed the previous topics in this course, specifically "Setting up the Haskell environment (GHC, GHCi, Stack, Cabal)". **Step 1: Install Haskell** If you haven't already, install Haskell on your machine by following the instructions on the [official Haskell website](https://www.haskell.org/downloads/). You can install Haskell using the Haskell Platform, which includes the Glasgow Haskell Compiler (GHC) and other essential tools. For this lab, we will be using the GHC compiler. Once installed, verify that GHC is working by opening a terminal and typing: ```bash ghc --version ``` **Step 2: Write a Simple Haskell Program** Create a new file called `HelloWorld.hs` using your favorite text editor or IDE. In this file, write the following Haskell program: ```haskell -- This is a simple Haskell program that prints "Hello, World!" to the console. main :: IO () main = putStrLn "Hello, World!" ``` Let's break down the syntax of this program: * `--`: This is a comment in Haskell. Anything following the `--` symbol on a line is ignored by the compiler. * `main :: IO ()`: This is the type signature for the `main` function. In Haskell, every function has a type signature that specifies its input and output types. In this case, `main` takes no input (hence the `()` type) and returns an `IO` action. * `main = putStrLn "Hello, World!"`: This defines the `main` function. `putStrLn` is a function that takes a string as input and prints it to the console, followed by a newline character. **Step 3: Run the Haskell Program** To run the Haskell program, open a terminal and navigate to the directory where you saved `HelloWorld.hs`. Then, type the following command: ```bash ghc HelloWorld.hs ``` This will compile the Haskell program and produce an executable file called `HelloWorld`. To run the program, type: ```bash ./HelloWorld ``` You should see the following output: ``` Hello, World! ``` **Conclusion** In this lab, you installed Haskell on your machine, wrote a simple Haskell program, and ran it using the GHC compiler. You learned about the basic syntax of Haskell, including comments, type signatures, and function definitions. You also learned how to compile and run a Haskell program. **Key Takeaways:** * Haskell is a statically typed language, which means you must specify the type of every variable and function before using it. * Haskell uses a whitespace-sensitive syntax, which means you must indent your code correctly for it to be parsed correctly. * You can use `ghc` to compile and run Haskell programs, or use an IDE like Visual Studio Code or IntelliJ IDEA for a more convenient development experience. **Practice Exercise:** 1. Modify the `HelloWorld` program to print out your name instead of "Hello, World!". 2. Write a new Haskell program that takes a name as input from the user and prints out a personalized greeting. **External Resources:** * [Official Haskell Documentation](https://www.haskell.org/documentation) * [Haskell Tutorial by Real World Haskell](https://book.realworldhaskell.org/read/) * [Haskell for Imperative Programmers ( tutorial by Greg Weiss)](http://learnyouahaskell.com/chapters) Please take the time to try the practice exercise and review the material before proceeding to the next topic. If you have any questions or need help with anything, please leave a comment below. Our next topic will be 'Primitive types in Haskell: Int, Float, Bool, Char, String.' This topic is part of the 'Basic Types, Functions, and Pattern Matching', which will cover the different types of data available in Haskell and how you can use them to represent and manipulate data in your programs.