Clockwork Clojure: A Protocol-Powered Runtime for Composable Evaluation - Ferri

Paolo Ferri demonstrates Clockwork, a protocol-driven Clojure runtime hosted in Swift that enables a live REPL on iOS.

What if Clojure’s core semantics were modular, pluggable, and inspectable? Clockwork is a protocol-driven Clojure runtime hosted in Swift, rebuilt from first principles with no shortcuts. By abstracting effects and treating evaluation as data, we gained a live REPL on iOS plus a fully flexible evaluation substrate. Namespaces become dynamic, versioned mappings; macros evolve into remote, queryable services; interpreters, compilers, and pretty-printers swap on the fly. In this talk, you’ll see Clockwork demos that include: Live REPL-driven UI iteration on mobile Remote namespace hydration from Redis and Git Macro server with expansion tracing and visualization Hot-swapping evaluation strategies without breaking code Attendees will discover patterns for designing their own pluggable runtimes and DSLs, and witness how composable evaluation unlocks new horizons for Clojure tooling—on any platform. But this talk goes beyond demos: we’ll explore how protocol-based design empowers developers to rethink evaluation itself—turning it into a modular, inspectable, and swappable foundation. Whether you’re building a DSL, crafting runtime tooling, or transplanting Clojure’s interactive power into new environments, composable evaluation offers a transformative approach. Biography Paolo Ferri is a runtime designer, language hacker, and unapologetic lover of clean semantics. He’s spent the last year crafting a protocol-powered Clojure runtime that reshapes evaluation into a pluggable, composable architecture—with no shortcuts, no magic, just gears and grace. The result? Clockwork: a native Clojure runtime that interprets, hydrates, compiles, and hot-swaps its semantics seamlessly across platforms. Built in Swift from first principles, Clockwork runs a live REPL on iOS and supports macro servers, dynamic namespace hydration, and hot-swappable interpreters—all from pure Clojure code. Paolo’s philosophy? Architecture should move like a sonnet and hum like a well-oiled machine—precision earned in the quiet cafes and winding alleys of northern Italy, where beauty is non-negotiable and precision expected. He’s here to share Clockwork not as a personal achievement, but as an invitation—to rethink what a runtime can be when clarity wins, evaluation and effects are composable, and the REPL lives anywhere imagination can reach. Recorded Nov 13, 2025 at Clojure/Conj 2025 in Charlotte, NC.