Schooner - An embeddable r7rs scheme

ausimian

Schooner is a sandboxed Scheme interpreter you embed in an Elixir app (like Lua/Luerl but with more parentheses). It targets r7rs-small minus its mutable operations — no set!, set-car!, vector-set!, etc. — which keeps the value model immutable and friendly to BEAM idioms. The host hands a script source to Schooner.eval/2, gets back a tagged Elixir term, and resource-bounds the work with the standard process tools (:max_heap_size, Task.shutdown/2).

alias Schooner.Host

env =
  Schooner.Environment.new(
    libraries: [
      Host.library(
        primitives: [
          {"shout", 1, fn [msg] ->
             text = msg |> Host.to_string!(op: "shout") |> String.upcase()
             Host.string(text <> "!")
           end}
        ]
      )
    ]
  )

Schooner.eval(~s|(import (scheme base)) (shout (string-append "hello, " "world"))|, env)
# => {:ok, "HELLO, WORLD!"}

It implements most of r7rs-small, the deviations are listed in the documentation.

https://github.com/ausimian/schooner

3 comments

#library #libraries #schooner

8 839 3

2026-10-04 23:36:46 UTC

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kip

ex_cldr Core Team

As someone who grew up with Maclisp and John McCarthy I find this unreasonably exciting. And much more of a mental model that works for me than Lua. Thanks for making this happen - I’ll be sure to give it a spin on something. In fact I’ll just have to invent something so I can use it

I still think the Moonual is one of the best technical manuals ever written. It was my reference during many late night session on the System-M Multics system. Multics, Maclisp and Emacs were probably why I got hooked on computing.

Post #1

ausimian

I published 1.1.0 of Schooner. Its a mixture of performance improvements, docs tidy up and bug fixes.

The details are in the changelog.

Post #2

ausimian

I published 1.2.0 of Schooner. This was mostly improvements to tooling, notably:

Source locations in errors (yay)
Backtraces in errors
A mix task, schooner.check that will check (but not run) your scripts for unbound names, incorrect arity calls etc
A mix task, schooner.expand that will expand macro definitions
A mix task schooner.repl that will drop you into a repl where you can load scripts and evaluate expressions - from the tooling docs:

mix schooner.repl --env MyApp.Scripts.environment --load scripts/pricing.scm
Schooner 1.1.0 — environment: MyApp.Scripts.environment/0. ,help for commands.
schooner> (line-total "widget" 3)
30
schooner> (define (with-shipping x)
     ...>   (+ x 5))
schooner> (with-shipping 30)
35
schooner> (char-upcase #\a)
error: unbound variable: char-upcase
schooner> (import (scheme char))
schooner> (char-upcase #\a)
#\A
schooner> ,env unit
unit-price  (myapp catalog)  procedure, 1 arg
schooner> ,expand (when ok (go))
(if ok (begin (go)))
schooner> ,time (order-total '(("widget" . 2) ("gadget" . 1)))
30  ; 0.1ms, 1650 reductions
schooner> ,quit

Post #3

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