Toward safe, flexible, and efficient software in Common Lisp - European Lisp Symposium 2025

Caption notes

Robert Smith introduces Coalton, a statically typed language embedded in Common Lisp, through the practical demands of team maintenance and numerical software. A fast Fourier transform example compares type declarations, generic arithmetic and compiler optimization, then extends the algorithm to finite-field arithmetic. Monomorphization specializes generic source for concrete types, moving some runtime work into compilation. Smith also describes its costs. Source code or a suitable representation must be available, generated code can grow, and performance depends on the application. The later discussion and Q&A cover the standard library, editor support, Lisp interoperability and redefinition. He explicitly acknowledges an unresolved type-soundness issue involving polymorphism and mutation at the time of the talk. His timings illustrate particular examples and should be evaluated within that scope.