What Are Some Examples of Large Codebases Written in Lisp?

During my thesis work, I utilized Scheme, a dialect of Lisp, for my research tools. The model codebase I worked on exceeded 53,000 lines, while the analysis portion was approximately half that size. Excluding external libraries, the total was considerable, showcasing the scalability of Lisp in complex projects.

LISP Usage in Major Software Projects

The astronomical scheduling software for both the Hubble and upcoming Webb telescopes incorporates a substantial Lisp component, although the exact size is unknown. During my tenure at two companies, I encountered Lisp cores of significant size: one with 40,000 lines of code (loc) for analyzing health insurance claims, and another with 100,000 loc for resource scheduling.

Other notable usages of Lisp include:

Interleaf: This publishing tool, especially used at NASA, is a testament to Lisp's versatility in handling complex tasks. Its development and maintenance likely demanded a large codebase.

Grammarly: The core functionality of Grammarly, including Natural Language Processing (NLP) tasks, is powered by Lisp. The company even advertises jobs related to Lisp.

Orbitz: While the specific details are limited, it is known that Orbitz utilized Lisp for its core functionality, though some C or C was used for in-memory databases for performance reasons.

Although Google is often perceived as having purged Lisp from its system after acquiring the company, it retains a significant number of programmers who are comfortable with the language. This is evident from the availability of Lisp jobs within the company and the fact that a considerable number of Google engineers are known Lisp enthusiasts.

In-House Applications at Defense Contractors

A large proportion of Lisp usage remains hidden within defense contractors. Internal systems, though rarely publicized, represent some of the largest Lisp codebases. Companies often have job postings that hint at the presence of Lisp, indicating that it plays a crucial role in their in-house projects.

Other Significant Uses of Lisp

One specific application of Lisp that exemplifies its flexibility is Emacs Lisp. Emacs itself has a core written in C, but the majority of its functionality is provided by modules written in Emacs Lisp. This allows for extensive customization and extension, making Emacs a prime example of a large, complex Lisp codebase. If you use Emacs, you might find yourself spending countless hours customizing and improving its Lisp-based modules.

Conclusion: Lisp continues to demonstrate its value in large-scale software development across a wide range of industries, from astronomy and healthcare to publishing and web development. Its scalability and flexibility make it an excellent choice for complex, long-term projects.