Getting Started
What Is Functional Programming? A Beginner's Guide
New to functional programming? Learn what it is, why it matters, and how it differs from imperative and object-oriented...
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Define Your Knowledge. Master Functional Programming.
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defun.info is an educational resource for developers learning functional programming. Explore in-depth guides, tutorials, and articles on Lisp, Common Lisp, Clojure, Haskell, Elixir, Emacs Lisp, and functional programming concepts like immutability, higher-order functions, recursion, and more.
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Language Guides
Clojure vs Haskell: Which Functional Language Should You Learn?
Clojure and Haskell are two of the most popular functional languages. Here's how they compare in philosophy,...
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Core Concepts
Pure Functions and Side Effects: The Heart of Functional Programming
Understand what pure functions are, why side effects matter, and how separating the two leads to cleaner, more testable...
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Emacs & Tooling
Setting Up Emacs for Clojure Development with CIDER
Learn how to configure Emacs and CIDER for a powerful Clojure REPL-driven development environment from scratch.
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Core Concepts
Higher-Order Functions Explained: map, filter, and reduce
Master the three most important higher-order functions in functional programming — map, filter, and reduce — with...
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Projects & Patterns
Building a Todo CLI App in Elixir: A Functional Project Walkthrough
Walk through building a command-line todo application in Elixir to learn functional patterns, pattern matching, and...
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Getting Started
Beginner-friendly introductions to functional programming, setting up your environment,...
ExploreLanguage Guides
Deep-dive guides into Lisp, Common Lisp, Clojure, Haskell, Elixir, and other functional...
ExploreCore Concepts
Explanations of foundational functional programming ideas: immutability, pure functions,...
ExploreEmacs & Tooling
Guides on Emacs Lisp, SLIME, CIDER, REPLs, and the developer tooling ecosystem for...
ExploreProjects & Patterns
Real-world project walkthroughs, design patterns, and architectural approaches using...
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