Fun Programming Language Documentation

Welcome to the Fun programming language! Fun is a purely functional programming language with type inference, built in Go with Tree-sitter parsing and LSP support.

Quick Navigation

• Language Guide - Learn the Fun language syntax and features
• Type System - Understanding Hindley-Milner type inference
• Standard Library - Built-in functions and types
• Modules - Code organization and imports
• REPL Guide - Interactive development environment
• IDE Support - VS Code extension and LSP features
• Examples - Code examples and tutorials
• Internals - Language implementation details

What is Fun?

Fun is a functional programming language designed for:

• Type Safety: Hindley-Milner type inference with polymorphic types
• Functional Programming: Lambda expressions, pattern matching, immutable data
• Developer Experience: REPL, LSP support, VS Code integration
• Performance: Tree-sitter parsing, efficient evaluation

Key Features

Functional Programming

• Lambda expressions: \x -> x + 1
• Pattern matching with when expressions
• Immutable data structures
• Higher-order functions

Type System

• Automatic type inference
• Polymorphic types
• Type annotations when needed
• Compile-time type checking

Developer Tools

• Interactive REPL
• Language Server Protocol
• VS Code extension
• Syntax highlighting

Getting Started

1. Install: Clone and build the project
2. Try REPL: Run ./fun for interactive development
3. Run Programs: ./fun examples/basic/main
4. IDE Setup: Install the VS Code extension

Example

import lib from `./lib`

# computes the sum of integers from 1..n
sum_range : Lam<Int, Int>
sum_range = fix(\rec -> \n ->
    when n == 0 is
        True t -> 0;
        False f -> n + rec(lib.dec(n))
)

sum_range(100) # result: 5050

Community

• Author: Matan Tsuberi tsuberim@gmail.com
• License: MIT
• Repository: GitHub

---

Start with the Language Guide to learn Fun programming!