Jolt is a self-hosted Clojure implementation that runs on Scheme — Chez natively, Gambit for JavaScript. No JVM, no build step — most portable Clojure runs unchanged.
- The compiler is written in Clojure and compiles itself
- Persistent data, lazy seqs, transducers, multimethods, protocols — full Clojure semantics
- Real concurrency:
future,agent,pmap, andcore.asyncon OS threads jolt buildemits a single standalone binary — no Scheme or JVM needed to run it
The terminal on the right is jolt itself — compiled to JavaScript by the Gambit backend — evaluating live in your browser. It runs a reduced build to keep the download small, so regex is left out here and says so if you reach for it.
jolt via Gambit → JS repl
user=> (->> (range 10) (filter even?) (map #(* % %)) (reduce +))
120
Why Jolt?
Self-Hosted Compiler
Reads Clojure, analyzes it to a host-neutral IR, emits Scheme, and runs it — on Chez natively, or on Gambit compiled to JavaScript. The compiler is written in Clojure and compiles itself.
Standalone Binaries
jolt build ahead-of-time compiles a project — runtime, standard library, app, and its deps — into a single self-contained executable. No Chez, no JVM, no source needed to run it.
Real Concurrency
future/promise/agent/pmap run on OS threads over a shared heap, matching JVM semantics. core.async provides channels and go blocks.
Full Numeric Tower
Exact integers and bignums, exact ratios ((/ 1 2) ⇒ 1/2), and flonum doubles. = is category-aware; == is value-equality.
Persistent Data
Immutable vectors (32-way tries), cons lists, and HAMT maps/sets with Clojure value semantics. Transients are real mutable scratch collections.
Clojure-Compatible
Lazy/infinite seqs, transducers, destructuring, multimethods, protocols/records, metadata, namespaces, runtime eval, and the full reader.
Quick Start
Install the self-contained jolt binary — it bundles the runtime, compiler, and standard library, so there's nothing else to install.
brew install jolt-lang/jolt/jolt
curl -sL https://raw.githubusercontent.com/jolt-lang/jolt/main/install | bash
jolt -e '(+ 1 2)' Or run from a clone (needs Chez Scheme) — no build step, the bootstrap seed is checked in:
git clone --recurse-submodules https://github.com/jolt-lang/jolt.git
cd jolt
bin/jolt -e '(+ 1 2)' Usage
Evaluate an expression
$ bin/jolt -e '(->> (range 10) (filter even?) (map (fn [x] (* x x))) (reduce +))'
$ bin/jolt -e '(/ 1 2)'
Run a project
bin/jolt run -m myapp.core
bin/jolt -M:test [args]
bin/jolt path Compile a standalone binary
bin/jolt build -m myapp.core -o myapp
./myapp arg1 arg2
nREPL
bin/jolt --nrepl-server
Develop against a live process: see REPL-Driven Development.
Read the documentation for installation, writing libraries, and host interop.
Differences from Clojure
Jolt targets Clojure semantics but runs on Scheme, not the JVM. Most portable Clojure runs unchanged — persistent collections, the numeric tower, lazy seqs, transducers, multimethods, protocols/records, atoms, future/agent/pmap, core.async, runtime eval, and the full reader all behave as on the JVM. The genuine divergences:
| Aspect | Difference |
|---|---|
| Java interop | No JVM, so no general Java interop, reflection, or gen-class/proxy — a shimmed subset of java.* is available, plus a C FFI |
| BigDecimal | Not available (decimal? is always false); the rest of the numeric tower matches |
| Regex | Compiled by irregex, not java.util.regex — common patterns work, some Java-specific features differ |