The European Lisp Symposium (ELS) is an annual academic conference dedicated to the Lisp family of programming languages, including Common Lisp, Scheme, Clojure, and related dialects. It serves as a forum for researchers, practitioners, and enthusiasts to present original work on Lisp language design, implementation, applications, and the history and culture of Lisp. The symposium typically features paper presentations, keynote talks, tutorials, and workshops, and it rotates among European venues.
1 History
1.1 Origins
The European Lisp Symposium was established in 2008 to fill a gap in the European conference landscape for Lisp‑oriented research and development. Prior to its founding, the main dedicated Lisp event was the International Lisp Conference (ILC), which was held primarily in North America. A group of European Lisp researchers and enthusiasts, motivated by the desire to create a regular, region‑focused venue, organized the first symposium in Paris, France. The founding committee sought to foster collaboration between academic and industrial Lisp users and to revitalize interest in Lisp dialects in Europe.
1.2 Editions and venues
1.2.1 Early years (2008–2012)
The first five editions of the symposium were held in major European cities: Paris (2008), Milan (2009), Lisbon (2010), Utrecht (2011), and Zürich (2012). These early conferences established the core format—single‑track paper sessions, invited keynotes, and social events—and attracted a small but dedicated community. Attendee numbers slowly increased, and proceedings were published online by the organisers. Notable early keynote speakers included Lisp pioneers such as Guy L. Steele Jr. and Richard P. Gabriel.
1.2.2 Recent editions (2013–present)
From 2013 onward, the symposium continued to rotate across Europe: Madrid (2013), Vienna (2014), London (2015), Kraków (2016), and Brussels (2017). In 2018 the symposium moved to Maribor, Slovenia, and subsequent editions have been held in Genoa (2019), virtual due to the COVID‑19 pandemic in 2020 and 2021, Bordeaux (2022), and Liège (2023). The 2024 edition is scheduled for Vienna. The number of submissions has grown steadily, and proceedings have been published by the ACM Digital Library and OpenAccess series since 2015.
2 Organization
2.1 Steering committee
The steering committee oversees the long‑term direction of the symposium, ensuring continuity across editions. It consists of senior researchers and practitioners from academia and industry who have been active in the Lisp community. The committee approves venue proposals, appoints program chairs, and maintains the symposium’s policies on reviewing and publication. Members serve staggered terms, typically four to six years.
2.2 Program committee
The program committee (PC) is responsible for reviewing and selecting submitted papers. Each year, a PC chair appoints a team of reviewers with expertise in Lisp‑related topics. The PC evaluates submissions based on originality, technical soundness, relevance, and clarity. The review process is single‑blind (reviewers are anonymous to authors). The PC typically meets virtually to finalize decisions and, for accepted papers, may suggest revisions.
2.3 Local organizing committee
Each host institution appoints a local organizing committee (LOC) that handles practical arrangements: venue booking, registration, audiovisual support, catering, and social events. The LOC works closely with the program chair and steering committee to ensure the symposium runs smoothly. Local organizers often include graduate students and faculty from the host university.
3 Scope and topics
3.1 Research areas
3.1.1 Language design and semantics
The symposium welcomes work on the design of new Lisp dialects or extensions to existing ones, as well as formal semantics for Lisp‑like languages. Topics include type systems (e.g., gradual typing for Common Lisp), macro systems, lexical scoping, and the integration of functional and object‑oriented paradigms. Papers in this area often present theoretical frameworks or formal proofs.
3.1.2 Implementation and compilation
Research on compilers, interpreters, virtual machines, and runtime systems for Lisp languages is a core area. This includes just‑in‑time (JIT) compilation, garbage collection, optimization techniques, and native code generation. Contributions may describe new implementations (e.g., SBCL internals, Clojure’s hosting on the JVM) or improvements to existing systems.
3.1.3 Formal methods and verification
Formal verification of Lisp programs and systems, including symbolic execution, theorem proving, and model checking, is a recurring topic. Researchers present methods for proving correctness of Lisp code, reasoning about macros, or verifying safety properties of Lisp‑based software. The use of Lisp for theorem provers (e.g., ACL2) is also discussed.
3.2 Applied Lisp
3.2.1 Web development and systems programming
Practical uses of Lisp in modern software engineering are represented. This includes web frameworks (e.g., Hunchentoot, Clack), REST APIs, database interaction, and systems‑level programming on embedded platforms. Papers may describe deployment experiences or performance benchmarks.
3.2.2 Artificial intelligence and symbolic computation
Given Lisp’s historical role in AI, the symposium continues to cover symbolic AI, knowledge representation, natural language processing, and rule‑based systems. Recent work also includes machine learning with Lisp‑based libraries (e.g., mgl, cl‑ml) and integration with deep‑learning frameworks.
3.2.3 Domain‑specific languages
Lisp’s macro system is often used to create domain‑specific languages (DSLs) for various applications—from configuration languages to scientific computing. Papers in this area present new DSLs, discuss design patterns, or evaluate the expressiveness of Lisp for DSL construction.
4 Program format
4.1 Keynote speeches
Each symposium features one or two invited keynote talks by prominent figures in the Lisp world or related fields. Keynotes cover broad topics such as the history of Lisp, future directions for the language family, or interdisciplinary connections (e.g., Lisp and hardware design). Past keynoters include Gerald Jay Sussman, Christian Queinnec, and Rich Hickey.
4.2 Paper sessions
4.2.1 Reviewed research papers
Full papers (typically 10–16 pages) undergo rigorous peer review. Accepted papers are presented in 25‑minute sessions (20 minutes talk + 5 minutes Q&A). The proceedings are published and indexed in academic databases. Since 2015, ELS proceedings have been included in the ACM International Conference Proceedings Series.
4.2.2 Lightning talks
Short presentations (5 minutes each) allow participants to share work‑in‑progress, demonstrators, or small ideas without the overhead of a full paper submission. Lightning talks are selected on‑site or via a lightweight proposal process. They often generate lively discussion and are a popular element of the symposium.
4.3 Tutorials and workshops
Half‑day or full‑day tutorials are offered on topics such as Common Lisp tooling, ClojScript for front‑end development, or advanced macro techniques. Workshops (e.g., the "Lisp Game Jam" workshop) provide hands‑on collaborative sessions. Tutorials and workshops may be held on the day before the main symposium.
4.4 Social events
Social activities are an integral part of ELS, fostering community building. These include a welcome reception, a conference dinner (often in a local restaurant or historic venue), and informal hacking sessions. Many editions also feature a "birds‑of‑a‑feather" (BoF) session where attendees self‑organize discussions around specific interests.
5 Impact and community
5.1 Role in the Lisp ecosystem
The European Lisp Symposium has become the primary European venue for Lisp‑related research and application. It bridges the gap between academic research and practical industrial use, encouraging contributions from both university labs and companies. The symposium has helped sustain and grow the Lisp community in Europe, providing a regular meeting point for enthusiasts and professionals. Several open‑source projects (e.g., the Common Lisp implementation SBCL, the Quicklisp package manager) have been discussed and advanced at ELS.
5.2 Relationship to other conferences
5.2.1 International Lisp Conference (ILC)
The International Lisp Conference (ILC), historically held in the United States, is the sister event of ELS. The two conferences share similar scopes but target different geographic regions. In some years, the ILC and ELS have coordinated to avoid scheduling conflicts, and a few researchers have presented at both. The steering committees maintain informal contact, but there is no formal merger or joint organization.
5.2.2 Lambda‑the‑Ultimate
Lambda‑the‑Ultimate (LtU) is a popular community blog and discussion site for programming language theory and practice, with strong Lisp representation. ELS often draws participants from the LtU community, and many paper announcements or post‑symposium discussions appear there. However, LtU is not a conference and does not publish proceedings; it serves as a complementary forum for ongoing dialogue.