@borkdude/sci

Small Clojure Interpreter

A tiny implementation of Clojure in Clojure.

Rationale

You want to evaluate code from user input, but eval isn't safe or simply doesn't work.

This library works with:

• Clojure on the JVM
• Clojure compiled with GraalVM native
• ClojureScript, even when compiled with :advanced

It is used as the interpreter for babashka.

Status

Experimental. Breaking changes are expected to happen at this phase.

Installation

Use as a dependency:

Usage from Clojure and ClojureScript

(require '[sci.core :as sci])
(sci/eval-string "(inc 1)") => ;; 2
(sci/eval-string "(inc x)" {:bindings {'x 2}}) ;;=> 3

Usage from JavaScript

const { evalString } = require('@borkdude/sci');
const f = evalString("(fn [obj] (-> obj js->clj frequencies clj->js))")
> f(["foo", "bar", "foo"]);
{ foo: 2, bar: 1 }

Currently the following special forms/macros are supported: def, fn, function literals (#(inc %)), defn, quote, do,if, when, cond, let, and, or, ->, ->>, as->, comment, loop, lazy-seq, for, doseq, case.

In sci, defn does not mutate the outside world, only the evaluation context inside a call to sci/eval-string.

By default sci only enables access to the pure non-side-effecting functions in Clojure. More functions can be enabled, at your own risk, using :bindings:

user=> (sci/eval-string "(println \"hello\")" {:bindings {'println println}})
hello
nil

More examples of what is currently possible can be found at babashka.

Caveats

To make the rand-* functions behave well when compiling to a GraalVM native binary, use this setting:

--initialize-at-run-time=java.lang.Math\$RandomNumberGeneratorHolder

Test

Required: lein, the clojure CLI and GraalVM.

To succesfully run the GraalVM tests, you will have to compile the binary first with script/compile.

To run all tests:

script/test/all

For running individual tests, see the scripts in script/test.

License

Copyright © 2019 Michiel Borkent

Distributed under the Eclipse Public License 1.0. This project contains code from Clojure and ClojureScript which are also licensed under the EPL 1.0. See LICENSE.