Haskell LYAH – Learn You a Haskell Exercise Collection

A comprehensive, hands-on companion to the classic "Learn You a Haskell for Great Good!" book. This repository contains carefully crafted exercises for each chapter, designed to reinforce concepts through practical coding challenges.

📚 What's Inside

This project follows the structure of LYAH chapter by chapter, with each topic containing:

• README.md – Exercise descriptions with examples and hints
• Exercises.hs – Completed solutions with type signatures and implementations

Each exercise set is designed to:

• Reinforce the core concepts from the corresponding chapter
• Progressively build complexity
• Encourage functional thinking and pattern matching
• Provide immediate, testable examples

🗂️ Repository Structure

haskell-lyah/
│
├── 02-starting-out/
├── 03-types-and-typeclasses/
├── 04-syntax-in-functions/
├── 05-recursion/
├── 06-higher-order-functions/
├── 07-modules/
├── 08-making-our-own-types-and-typeclasses/
├── 09-input-and-output/
├── 10-functionally-solving-problems/
├── 11-functors-applicative-functors-and-monoids/
├── 12-a-fistful-of-monads/
├── 13-for-a-few-monads-more/
└── 14-zippers/

Each directory contains 8-15 exercises that target the chapter's key topics.

🎯 Exercise Philosophy

The exercises in this repository follow these principles:

1. Concept-First: Each exercise isolates and reinforces a specific concept
2. Progressive Difficulty: Starts simple, builds to more complex applications
3. Practical Examples: Real-world inspired problems, not abstract puzzles
4. Type-Driven: Emphasizes thinking with types before implementing
5. Self-Contained: Each exercise can be understood and solved independently

🚀 Getting Started

Prerequisites

• GHC (Glasgow Haskell Compiler) 8.10 or newer
• Basic familiarity with "Learn You a Haskell" content

Running the Exercises

# Navigate to any topic directory
cd 05-recursion

# Load the exercises in GHCi
ghci Exercises.hs

# Test individual functions
> quickSort [3,1,4,1,5,9]
[1,1,3,4,5,9]

Workflow Recommendation

1. Read the corresponding LYAH chapter
2. Open the topic's README.md to view exercises
3. Attempt to solve them yourself first
4. Compare with the solutions in Exercises.hs
5. Experiment and modify the code in GHCi

📖 Topics Covered

• Starting Out: Basic syntax, lists, ranges, list comprehensions
• Types and Typeclasses: Type system fundamentals, common typeclasses
• Syntax in Functions: Pattern matching, guards, where/let bindings
• Recursion: Recursive thinking, edge cases, accumulator patterns
• Higher-Order Functions: Maps, filters, folds, function composition
• Modules: Importing, qualified imports, Data.List, Data.Map
• Custom Types: Data declarations, record syntax, type parameters
• I/O: Actions, do notation, file handling
• Problem Solving: Reverse Polish notation, pathfinding algorithms
• Functors & Applicatives: Functor laws, applicative operations, monoids
• Monads: Maybe, list, IO monads, monad laws
• Monad Transformers: State, Reader, Writer monads
• Zippers: Focus-based navigation, tree zippers, functional cursors

🤝 Contributing

This is a personal learning repository, but suggestions and corrections are welcome! If you find errors or have ideas for additional exercises, feel free to open an issue or submit a pull request.

📝 License

This project is released into the public domain under the Unlicense. Feel free to use, modify, and distribute this code however you like.

🙏 Acknowledgments

• Miran Lipovača for writing the excellent "Learn You a Haskell for Great Good!"
• The Haskell community for making functional programming accessible and enjoyable

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