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Cyclone Scheme

Travis CI

Github CI - Linux

Github CI - MacOS

Github CI - MacOS Homebrew

Github CI - Windows

Cyclone Scheme is a brand-new compiler that allows real-world application development using the R7RS Scheme Language standard. We provide modern features and a stable system capable of generating fast native binaries.

Cheney on the MTA is used by Cyclone's runtime to implement full tail recursion, continuations, and generational garbage collection. In addition, the Cheney on the MTA concept has been extended to allow execution of multiple native threads. An on-the-fly garbage collector is used to manage the second-generation heap and perform major collections without "stopping the world".


  • Support for the majority of the Scheme language as specified by the latest R7RS standard.
  • New features from R7RS including libraries, exceptions, and record types.
  • Built-in support for Unicode strings and characters.
  • Hygienic macros based on syntax-rules
  • Low-level explicit renaming macros
  • Guaranteed tail call optimizations
  • Native multithreading support
  • A foreign function interface that allows easy integration with C
  • A concurrent, generational garbage collector based on Cheney on the MTA
  • Includes an optimizing Scheme-to-C compiler,
  • ... as well as an interpreter for debugging
  • A Package Manager and a growing list of packages.
  • Support for many popular SRFI's
  • Online user manual and API documentation
  • Support for Linux, Windows, FreeBSD, and Mac platforms.
  • Known to run on x86-64, x86, and Arm (Raspberry Pi) architectures.

Try in your Browser

You can run the Cyclone interpreter right in your browser. No installation required.


For the full user experience - compiling files, installing packages, running native code, etc - it is necessary to install a copy of Cyclone.

There are several installation options available:



Cyclone can be run from a Docker Image:

docker run -it cyclonescm/cyclone bash



Mac (and Linux!) users wanting to use Homebrew can do the following.

Note if Homebrew is not already installed: follow the instructions at to install the homebrew package manager.

brew tap cyclone-scheme/cyclone
brew install cyclone-scheme/cyclone/cyclone-bootstrap

Arch Linux

Arch Linux

Arch Linux users can install using the AUR:

git clone
cd cyclone-scheme
makepkg -si

Gentoo Linux

Gentoo Linux

Cyclone is available from the official Gentoo package repository.

Build from Source

Build from Source

To install Cyclone on your machine for the first time on Linux, Windows, FreeBSD, and for Mac users wanting to install without using Homebrew, use cyclone-bootstrap to build a set of binaries. Instructions are provided for Linux, Mac, Windows (via MSYS), and FreeBSD 12.

Getting Started

After installing you can run the cyclone command to compile a single Scheme file:

$ cyclone examples/fac.scm
$ examples/fac

And the icyc command to start an interactive interpreter. Note you can use rlwrap to make the interpreter more friendly, EG: rlwrap icyc:

$ icyc

       @@     @@     Cyclone Scheme->C compiler
       @@     #@     (c) 2014-2019 Justin Ethier
       `@@@#@@@.     Version 0.11
cyclone> (write 'hello-world)

Read the documentation below for more information on how to use Cyclone.

Package Manager

Cyclone Winds

The winds package manager provides the ability to install packaged libraries and programs for Cyclone. See the winds site for more information.

The Winds wiki contains a full list of packages with documentation.


Example Programs

Cyclone provides several example programs, including:

  • Tail Call Optimization - A simple example of Scheme tail call optimization; this program runs forever, calling into two mutually recursive functions.

  • Threading - Various examples of multi-threaded programs.

  • Game of Life - The Conway's game of life example program and libraries from R7RS.

  • Game of Life PNG Image Generator - A modified version of game of life that uses libpng to create an image of each iteration instead of writing it to console. This example also demonstrates basic usage of the C Foreign Function Interface (FFI).

  • Finally, the largest program is the compiler itself. Most of the code is contained in a series of libraries which are used by cyclone.scm and icyc.scm to create executables for Cyclone's compiler and interpreter.

Compiler Internals

  • Writing the Cyclone Scheme Compiler provides high-level details on how the compiler was written and how it works.

  • There is a Development Guide with instructions for common tasks when hacking on the compiler itself.

  • Cyclone's Garbage Collector is documented at a high-level. This document includes details on extending Cheney on the MTA to support multiple stacks and fusing that approach with a tri-color marking collector.


Copyright (C) 2014 Justin Ethier.

Cyclone is available under the MIT license.


🌀 A brand-new compiler that allows practical application development using R7RS Scheme. We provide modern features and a stable system capable of generating fast native binaries.




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