# Unison — A Content-Addressed Programming Language

> Unison is a statically typed functional programming language where code is stored as a content-addressed hash tree, eliminating dependency conflicts, enabling seamless distributed computing, and making refactoring trivial.

## Install

Save in your project root:

# Unison — A Content-Addressed Programming Language

## Quick Use
```bash
# Install UCM (Unison Codebase Manager)
curl -fsSL https://github.com/unisonweb/unison/releases/latest/download/ucm-linux.tar.gz | tar xz
./ucm
# Inside UCM:
.> pull @unison/base/main lib.base
```

## Introduction
Unison is a functional programming language that takes a fundamentally different approach to code management. Instead of storing code as text files, Unison identifies every definition by the hash of its syntax tree. This means renaming a function does not break dependents, dependency conflicts cannot exist, and code can be trivially shared or executed across distributed nodes.

## What Unison Does
- Stores code in a content-addressed codebase where definitions are identified by hash, not name
- Eliminates dependency hell because two versions of the same library can coexist without conflict
- Provides built-in support for distributed computing via its Abilities system (algebraic effects)
- Includes the Unison Codebase Manager (UCM) for browsing, editing, and sharing code
- Supports structural typing and pattern matching with a Haskell-inspired syntax

## Architecture Overview
The Unison Codebase Manager (UCM) is the central development tool. When you write Unison code in a scratch file, UCM watches for changes, typechecks the definitions, and stores them in a local SQLite-backed codebase keyed by content hash. Names are metadata attached to hashes, not identifiers. The runtime compiles Unison to an intermediate representation that runs on a custom virtual machine. The Abilities system (similar to algebraic effects) allows pure expression of side effects that can be interpreted differently in tests vs. production.

## Self-Hosting & Configuration
- Download the UCM binary from the official releases for Linux, macOS, or Windows
- The codebase is stored locally in `~/.unison` by default
- Pull libraries from Unison Share (share.unison-lang.org), the community package hub
- Use `ucm` commands to create namespaces, push/pull code, and run tests
- Scratch files (`.u` extension) are watched by UCM and typechecked on save

## Key Features
- Content-addressed storage makes all refactors (renames, moves) perfectly safe
- Abilities system provides typed, composable effect handling without monads
- Built-in test framework with `test>` watch expressions that run on save
- Distributed computing primitives let you describe computations that span multiple nodes
- Unison Share enables publishing and discovering libraries with no version conflicts

## Comparison with Similar Tools
- **Haskell** — similar syntax and type system, but Haskell uses traditional file-based modules; Unison's hash-based storage eliminates breakage from renames
- **Erlang/Elixir** — strong in distribution; Unison adds content-addressing and a typed effect system
- **Scala** — JVM functional language; Unison has a lighter runtime and novel codebase model
- **Darcs** — a VCS with patch theory; Unison applies similar ideas at the code-definition level rather than file level

## FAQ
**Q: Where is the source code stored if not in files?**
A: Definitions live in a content-addressed SQLite codebase. You write in scratch `.u` files, but UCM parses them and stores the hashed AST. Names are just metadata pointers to hashes.

**Q: Can I use Unison for production applications?**
A: Unison is maturing but still evolving. It is best suited for exploratory projects, distributed computing experiments, and developers interested in next-generation language design.

**Q: How do I share Unison code with others?**
A: Push your namespace to Unison Share with `push` in UCM. Others pull it into their codebase. Since code is content-addressed, there are no version conflicts.

**Q: Does Unison have an IDE?**
A: UCM is the primary interface. Editor plugins for VS Code provide syntax highlighting. The language server protocol (LSP) support is in development.

## Sources
- https://github.com/unisonweb/unison
- https://www.unison-lang.org

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Source: https://tokrepo.com/en/workflows/asset-f24282ac
Author: AI Open Source