Jolt

A Clojure implementation on Chez Scheme. Jolt reads Clojure source, analyzes it to a host-neutral IR, emits Scheme, and runs it on Chez. The compiler is self-hosted: it is written in Clojure (jolt-core/) and compiles itself. It ships a Clojure-compatible standard library.

Requirements

Only Chez Scheme (the gate invokes it as chez). The conformance gate additionally uses Clojure on the JVM as an oracle, but running jolt does not.

Build

There is no build step. The bootstrap seed (host/chez/seed/{prelude,image}.ss) is checked in, so a fresh clone runs immediately:

git clone --recurse-submodules https://github.com/jolt-lang/jolt.git
cd jolt
bin/joltc -e '(+ 1 2)'        # => 3

After changing a compiler source — the reader (host/chez/reader.ss), the analyzer/IR/backend (jolt-core/jolt/*.clj), or the clojure.core overlay (jolt-core/clojure/core/*.clj) — re-mint the seed:

make remint                   # iterates host/chez/bootstrap.ss to a byte-fixpoint

Run

bin/joltc -e EXPR             # evaluate a Clojure expression and print the result

$ bin/joltc -e '(->> (range 10) (filter even?) (map (fn [x] (* x x))) (reduce +))'
120
$ bin/joltc -e '(/ 1 2)'
1/2

Architecture

A small Chez runtime (host/chez/*.ss: value model, persistent collections, seqs, vars/namespaces, host interop) hosts a portable Clojure overlay split across two source roots by when they load:

• jolt-core/ is baked into the seed — the compiler (jolt-core/jolt/: reader/analyzer/IR/backend, plus jolt.main/jolt.deps) and clojure.core in dependency-ordered tiers (jolt-core/clojure/core/NN-*.clj). Changing anything here means re-minting the seed.
• stdlib/ loads lazily at runtime off the source roots — the rest of the standard library (clojure.string/set/walk/edn/pprint/…) plus the jolt.ffi host library. Editing these needs no re-mint.

bin/joltc loads the checked-in seed and the spine, then compiles and evaluates on Chez (read → analyze → IR → emit → eval). host/chez/bootstrap.ss rebuilds that seed from source on pure Chez; the build is a self-hosting fixpoint (a rebuild reproduces the checked-in seed byte-for-byte).

Differences from Clojure

Jolt targets Clojure semantics but runs on Chez, not the JVM.

• Host platform. No JVM, no reflection, no gen-class/proxy of Java classes. Interop syntax (Class., Class/static, .method) works against a shimmed subset of the java.* standard library, and a class token resolves to a name. See docs/host-interop.md for what's covered and how to register your own host classes from a library.
• Numbers. The full Scheme numeric tower, matching the JVM: exact integers and bignums, exact ratios ((/ 1 2) ⇒ 1/2), and flonum doubles. = is category-aware ((= 3 3.0) ⇒ false); == is value-equality ((== 3 3.0) ⇒ true). integer?/int? are exact integers, float?/double? are flonums, ratio? is an exact non-integer. No BigDecimal (decimal? is always false).
• Concurrency. future/promise/agent/pmap run on real OS threads over a shared heap, matching JVM semantics (not isolated-heap snapshots). Atoms use a per-atom mutex with JVM-style CAS. clojure.core.async provides blocking channels and go/<!/>!/alts!/timeout.
• Regex. Backed by irregex (vendored), PCRE/Java-style patterns.
• Collections. Immutable persistent vectors, cons lists, and HAMT maps/sets. Hash-map/hash-set iteration order is unspecified — use sorted-map/sorted-set when order matters. Transients are real mutable scratch collections.

Supported and Clojure-compatible: lazy/infinite sequences, transducers, destructuring, multimethods with hierarchies, protocols/records (deftype/defrecord/reify/extend-protocol), metadata, namespaces, runtime eval/load-string/defmacro, and the reader (#(), #_, #?, tagged literals, #"…").

Test

make test                     # the full gate
make corpus                   # conformance corpus vs the JVM-sourced spec
make unit                     # host-specific unit cases
make selfhost                 # bootstrap fixpoint (rebuild == checked-in seed)
make smoke                    # bin/joltc CLI smoke
make sci                      # load borkdude/sci's source through joltc (compat stress)
make ffi                      # HTTP-server GC-safety + http-client temp paths
make transient                # transient mutation + linear-time builds
make certify                  # JVM oracle (skips if clojure is absent)

The conformance corpus (test/chez/corpus.edn) is a host-neutral language spec whose expected values are sourced from reference JVM Clojure. See test/conformance/SPEC.md.

License

Eclipse Public License 1.0