Unison Modules: An Overview

Are you looking for a programming language that supports modular design and code reuse? Look no further than Unison, the revolutionary new language that is turning heads in the software development world. In this article, we'll take a closer look at Unison modules and how they can help developers streamline their codebase and build better software.

What are Unison modules?

At its core, Unison is designed around the idea of decentralized, modular development. Rather than writing code that is tightly coupled and difficult to modify, Unison encourages developers to build independent, reusable modules that can be combined as needed to create larger programs.

But what exactly is a Unison module? Put simply, a module is a self-contained piece of code that provides a set of functions or data types for other modules to use. Modules can be thought of as building blocks that can be combined in various ways to create more complex programs.

Declaring and using modules

To define a new module in Unison, you simply use the module keyword followed by the name of your module:

module MyModule where

-- module code goes here

Within a module, you can define functions, data types, and other values as needed. You can also import other modules using the import keyword:

module MyModule where

import OtherModule

-- module code goes here

To use a module in your code, you first need to import it using the import keyword. Once imported, you can use any of the functions or data types exported by the module:

import MyModule

-- use MyModule functions and data types here

Unison uses a unique approach to module loading and dependency management that ensures all modules are loaded and compiled in the correct order. This allows developers to focus on writing code rather than worrying about complex dependency graphs and build systems.

Versioning and dependency management

One of the biggest challenges in software development is managing dependencies between different modules and libraries. Unison addresses this challenge with its built-in support for versioning and dependency management.

When you define a new module, you can specify the version number using the syntax module <name> <version> where. This allows you to maintain multiple versions of a module simultaneously, ensuring that changes to one version do not break other modules that depend on it.

Unison also provides tools for automatically resolving dependencies between modules, making it easy to ensure that your codebase is always up to date and working correctly.

Testing and debugging

Of course, no software project would be complete without robust testing and debugging tools. Unison provides a suite of tools for writing and running tests, as well as debugging code.

To write tests for a module, you simply define some test functions that verify the behavior of the module's functions and data types. You can then run these tests automatically using the test command:

test module MyModule

Unison's debugging tools include a powerful interactive debugger that allows you to step through your code and inspect variables at runtime. This can be incredibly useful for tracking down hard-to-find bugs and optimizing your code for performance.


Unison modules are a powerful tool for building modular, reusable software that scales easily as your codebase grows. Whether you're building a small application or a large-scale system, Unison's module system makes it easy to design and compose code in a decentralized, flexible way.

So why not give Unison a try and see how it can help you streamline your development process and build better software? With its modern, flexible syntax and powerful module system, Unison is quickly becoming the go-to choice for developers who want to stay ahead of the curve.

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Written by AI researcher, Haskell Ruska, PhD (haskellr@mit.edu). Scientific Journal of AI 2023, Peer Reviewed