16428179fa
Reorganize the flat 49-file test/ into three layers (jpm test recurses, so all
are still discovered):
- test/unit/ white-box component tests (reader, evaluator, types,
persistent-map, lazy-seq, macro, interop, compiler)
- test/integration/ cross-cutting + regression batteries (conformance, jank,
sci-bootstrap/runtime, features, systematic-coverage, api,
core, namespaces, ported clojure suites) and
.../ports/ ported clojure/cljs test batches pending consolidation
- test/spec/ the behavioral contract (built out in following commits)
- test/support/harness.janet shared defspec table runner (cases compared via
Jolt's own =, with a :throws sentinel) + expect= helpers
Files moved with git mv (history preserved) and import paths fixed for depth.
jpm test green. README Test section updated.
Next: build out test/spec/ to cover the public API area-by-area, mining the
integration batteries and filling gaps.
112 lines
6.1 KiB
Markdown
112 lines
6.1 KiB
Markdown
# Jolt
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A Clojure interpreter running on [Janet](https://janet-lang.org). Jolt reads Clojure source, evaluates it with an interpreter written in pure Janet, and ships a Clojure-compatible standard library. The goal is a Janet-hosted [SCI](https://github.com/borkdude/sci) runtime — a minimal bootstrap that loads SCI's Clojure source as its standard library.
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## Build
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```bash
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git clone https://github.com/yogthos/jolt.git
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cd jolt
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git submodule update --init # pulls vendor/sci
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jpm build # compiles build/jolt
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```
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Requires Janet ≥ 1.36 and `jpm`.
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## Run
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```
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build/jolt # start a REPL
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build/jolt file.clj [args] # run a file (binds *command-line-args* and *file*)
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build/jolt -e EXPR [args] # evaluate EXPR and print the result
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build/jolt -h # help
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```
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The REPL accumulates multi-line forms until they balance:
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```
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user=> (defn fib [n] (if (< n 2) n (+ (fib (- n 1)) (fib (- n 2)))))
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#'user/fib
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user=> (map fib (range 10))
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(0 1 1 2 3 5 8 13 21 34)
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```
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Running a file evaluates its top-level forms:
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```
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$ echo '(println "hello" (* 6 7))' > hello.clj
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$ build/jolt hello.clj
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hello 42
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```
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## Use as a library
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```janet
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(use jolt/api)
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(def ctx (init))
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(eval-string ctx "(+ 1 2)") # → 3
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(eval-string ctx "(map inc [1 2 3])") # → [2 3 4]
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```
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`(init)` returns a context with `clojure.core` loaded. Each context is isolated; use separate contexts for separate environments.
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## Host interop
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Jolt exposes CLJS-style host interop through `.` on any Janet table or struct — a field holding a function is called with the receiver as the first argument:
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```clojure
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(def obj {:greet (fn [self name] (str "Hello " name))})
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(. obj greet "Alice") ; → "Hello Alice"
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(.-greet obj) ; field access (reader sugar for (. obj :greet))
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```
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Janet's standard library is reachable through `jolt.interop` (and the `jolt.shell` / `jolt.http` helpers built on it):
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```clojure
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(require '[jolt.interop :as j])
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(j/janet-type [1 2]) ; → :tuple
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(j/janet-table-keys {:a 1 :b 2}) ; → [:b :a]
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```
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## Differences from Clojure
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Jolt targets Clojure semantics but runs on Janet, not the JVM. The notable divergences:
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- **Host platform.** No JVM and no Java interop — `import`, `gen-class`, `proxy` of Java classes, and `java.*` are unavailable. `instance?` recognizes a small set of built-in types (`clojure.lang.Atom`, `Number`, `String`, …).
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- **Numbers.** Janet integers and doubles. `(/ 1 3)` is `0.3333…` and large products lose precision. No ratios or `BigDecimal` (`ratio?` is always false, `bigdec` falls back to a double); `bigint`/`biginteger` use Janet's 64-bit `int/s64`, not arbitrary precision. The auto-promoting `+'`/`-'`/`*'`/`inc'`/`dec'` are aliases for the plain ops, since Janet numbers don't overflow. `quot`/`rem`/`mod` follow Clojure's sign rules.
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- **Collections.** By default Jolt uses immutable persistent data structures: vectors are 32-way branching tries (structural-sharing persistent vectors with O(log₃₂ n) `conj`/`assoc`/`nth`), lists are persistent singly-linked cons cells (O(1) `conj`/`cons` prepend with structural sharing), and maps/sets are persistent hash structures. Value equality and sequence operations are Clojure-compatible, but hash-map/hash-set iteration order is unspecified and differs from Clojure — use `sorted-map`/`sorted-set` when order matters.
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- **Mutable build mode.** Jolt can be compiled to use fast Janet-native *mutable* collections instead, via a build-time flag: `JOLT_MUTABLE=1 jpm build` (default `jpm build` is immutable). In mutable mode vectors and lists share one mutable array representation (so `conj` mutates in place and appends, and `vector?`/`list?` no longer distinguish them) — a performance/looseness trade-off. The default immutable build has full Clojure value semantics.
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- **Concurrency / STM.** Single-threaded. No refs, `dosync`, agents, or `send`; `locking` evaluates its body without real locking. Atoms, volatiles, and delays are supported.
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- **Regex.** Compiled to Janet's PEG engine (Janet has no regex). Supported: capturing groups (`[whole g1 …]`), greedy and lazy quantifiers with backtracking, `(?:…)`, lookahead `(?=…)`/`(?!…)`, alternation, anchors `^ $ \b \B`, character classes, and the `(?i)` flag. Not supported: lookbehind, backreferences (`\1`), and named groups (`(?<name>…)`).
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- **Arrays.** Java-style arrays map onto Janet's native types: `byte-array` is a Janet buffer (contiguous, C-backed); `object-array`/`int-array`/`double-array`/etc. are Janet arrays. `aget`/`aset`/`alength`/`aclone` work over both.
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- **Not implemented.** JVM reflection, `proxy`, and the `clojure.repl`/`clojure.template` namespaces. Transients (`transient`/`conj!`/`persistent!`) work but are correctness-only aliases over the persistent collections (no in-place speedup).
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Supported and Clojure-compatible: chars as a distinct type, lazy/infinite sequences, transducers, destructuring, multimethods with hierarchies, protocols/records (`deftype`/`defrecord`/`reify`/`extend-protocol`), metadata, namespaces, and the reader (`#()`, `#_`, `#?`, tagged literals, `#"…"`).
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## Test
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```
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jpm test # full suite (recurses test/)
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janet test/spec/sequences-spec.janet # a single spec
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janet test/integration/conformance-test.janet
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```
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Tests are organized in three layers:
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- **`test/spec/`** — the contract. Black-box, behavior-defining tables (one file
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per public API area) that collectively pin down Jolt's defined behavior. This
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is the authoritative description of what Jolt promises.
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- **`test/integration/`** — cross-cutting and regression batteries: the Clojure
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conformance suite, SCI bootstrap/runtime loading, jank conformance, and ported
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Clojure/CLJS test batches (`test/integration/ports/`).
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- **`test/unit/`** — white-box tests for individual components (reader,
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evaluator, types, persistent collections, regex, compiler).
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`test/support/harness.janet` provides the shared `defspec` table runner (cases
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are `["label" expected actual]`, compared with Jolt's own `=`) plus
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`expect=`/`expect-throws` for unit tests.
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## License
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[Eclipse Public License 1.0](https://opensource.org/licenses/EPL-1.0)
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