Introduction to Dhall: A functional configuration language

September 26, 2023

Configuration files are an integral part of software development, used to define parameters, settings, and options for applications. However, working with configuration files can sometimes be a daunting task, especially when they grow in complexity. In this blog post, we’ll explore a unique solution to this problem: The Dhall configuration language. We’ll discuss how Dhall combines functional programming principles with configuration files, making them more manageable, safe, and expressive.


What is Dhall?

Dhall is a functional programming language specifically designed for working with configuration files. Dhall aims to simplify the process of defining, managing, and using configuration data. It achieves this by providing a domain-specific language tailored for configuration purposes.


Functional Programming and configuration

Before we dive into Dhall’s features, let’s briefly discuss why functional programming is an excellent fit for configuration files:

  • Immutable Data: In functional programming, data is immutable, meaning it cannot be modified after creation. Configuration data is often treated as constant, making immutability a natural fit.
  • Pure Functions: Functional programming encourages pure functions that don’t have side effects. Configuration should not modify the application state but merely provide information, aligning with this functional principle.
  • Type Safety: Functional languages often have strong type systems, which ensure that data conforms to specific structures. This is crucial for configuration files to avoid unexpected errors.


Dhall’s key features



Dhall configuration files are designed to be human-readable and easy to understand. They use a concise syntax that eliminates redundancy and clutter, making configuration files more approachable.


Strong typing

Dhall enforces strong typing, ensuring that configuration data adheres to specified types. This eliminates type-related errors and provides clear expectations for data structure.


Hash-based verification

One of Dhall’s unique features is its hash-based verification. It generates a hash value for the configuration file content, which allows you to verify if any changes have occurred without needing to read and parse the entire file. This is especially useful for detecting modifications in large configuration files.


Security considerations

Dhall acknowledges security concerns and offers safety guarantees. It provides a “safety guarantees” page that outlines potential issues and considerations when using Dhall in security-critical applications.


Total programming

Dhall is designed as a “total programming language,” which means it guarantees that type checking and execution will complete in a finite amount of time. This prevents infinite loops and ensures predictable behavior.


Practical benefits

Dhall’s approach to configuration offers several practical benefits:

  • Simplified maintenance and readability of configuration files.
  • Reduced likelihood of configuration-related errors.
  • Improved security through hash-based verification.
  • Strong typing prevents type-related issues.
  • Compatibility with functional programming principles.



Configuration files are a crucial aspect of software development, and Dhall provides an innovative solution to manage them effectively. By combining functional programming principles with configuration data, Dhall simplifies the process, enhances security, and ensures maintainability. If you’re tired of dealing with cumbersome configuration files, exploring Dhall may be the solution you’ve been looking for.


Additional resources

Check out the Ada Beat Functional Programming blog for more topics, including functional programming principles, summaries of MeetUps, language specific articles, and much more. Whether you’re interested in functional programming theory or practical application, we have something for everyone.