Abstract:

This collection of articles from Planet Lisp showcases the vibrant activity within the Common Lisp community, covering a diverse range of topics from practical tutorials and library development to advanced experiments with modern AI. Several posts delve into the language's powerful features, such as creating robust macros using get-setf-expansion and foundational concepts like variable scoping. A significant theme is the extensive exploration of integrating Large Language Models (LLMs) with Common Lisp for sophisticated tasks like code generation, automated problem-solving, and in-depth code analysis. Other articles provide detailed tutorials on web development with the Ningle framework, announce major updates to libraries like FSet with new high-performance data structures, and introduce forward-looking projects like Web Embeddable Common Lisp (WECL) for running Lisp directly in the browser. These posts reflect a community actively applying Lisp's timeless principles to contemporary programming challenges.

A Summary of Recent Topics on Planet Lisp

• @2025-10-08 Advanced Macro Debugging: Tim Bradshaw introduces an update to his trace-macroexpand tool, adding a *trace-macroexpand-per-line-prefix* variable. This allows developers to prefix trace output, making it easier to distinguish from other program output when debugging complex macro expansions.

• @2025-10-07 Correctly Handling Lisp "Places": In a detailed technical post, Tim Bradshaw explains how to properly write a macro that provides a default value to a Common Lisp "place." He demonstrates how a naive approach can fail due to multiple evaluation and shows that the correct, robust solution requires using the get-setf-expansion function to correctly handle the structure of place forms.

• @2025-10-04 Community Infrastructure Update: Zach Beane posts a brief update confirming that the Planet Lisp meta-blog is back online and refreshing with new content after a recent server migration.

• @2025-10-02 Exploring AI and Lisp Programming Philosophies: Joe Marshall conducts an experiment inspired by Richard Gabriel's "Worse is Better" essay. He prompts an LLM to generate solutions for Advent of Code problems using two different styles: a meticulous "MIT" style prioritizing correctness and a pragmatic "New Jersey" style prioritizing implementation simplicity. The analysis reveals that the code generated with the "MIT" prompt was consistently judged as superior for its robustness, clarity, and maintainability.

• @2025-09-30 Web Development Tutorial - Building a Social App: Neil Munro provides Part 11 of a comprehensive tutorial on building a web application with the Ningle framework. This installment focuses on adding "post" and "like" functionality, covering database schema design with Mito, writing advanced queries with SXQL (using LEFT JOIN), separating controller logic for logged-in users with custom requirements, and integrating the backend with a dynamic frontend using JavaScript.

• @2025-09-29 Problem Solving with AI: Joe Marshall details his experience using the Gemini LLM to solve Advent of Code puzzles. By providing the LLM with a prompt to act as an "Elite Common Lisp developer" and forbidding the LOOP macro, he tested its ability to handle "word problems." The LLM successfully solved most of the first ten puzzles, demonstrating its capability for automated coding challenges, though it sometimes required hints.

• @2025-09-15 In-Depth Lisp Analysis with AI: Joe Marshall presents a system for analyzing Common Lisp code by feeding it to an LLM one top-level form at a time. This approach allows for granular feedback on code purpose, potential bugs, and adherence to best practices. The system provides the LLM with context and specific directives to generate insightful and actionable suggestions for improvement.

• @2025-09-19 FSet Library Gets a Performance Boost: Scott L. Burson announces a major update to the FSet functional collections library. Version 1.6.0 introduces sets and maps based on the CHAMP hash-based data structure, which provides significant performance gains over the previous weight-balanced trees, with lookups becoming nearly 5 times faster for larger collections.

• @2025-09-16 A Guide to Lisp Variables: Vindarel offers a detailed tutorial for newcomers on defining variables in Common Lisp. The post clearly explains the distinction between defparameter (for re-definable top-level parameters) and defvar (which protects variables from redefinition on reload), the use of let and let* for creating lexical scopes, and the *earmuffs* convention for dynamic variables.

• @2025-08-26 Self-Hosting and the "Minimum Clown Policy": Tim Bradshaw discusses his decision to move his Lisp code repositories off of GitHub to a self-hosted solution. Citing concerns about code being used for "AI slop," he advocates for a "minimum clown policy" where developers maintain control over their canonical data on infrastructure they manage, rather than relying on third-party platforms.

• @2025-08-21 Running Common Lisp in the Browser: TurtleWare presents the "Web Embeddable Common Lisp" (WECL) project, which enables scripting websites directly with Common Lisp. The post details the JS-FFI for low-level JavaScript interoperability and LIME/SLUG for interactive development from Emacs via a websocket connection to SLIME, demonstrating how to inject a CL runtime into arbitrary websites.