Scheme Implementations We Know

Note that this does not include all Scheme implementations, just those that we regularly use or keep around for other reasons. (And it probably doesn't even have all of those. Have patience while we add to this.) They are (sort-of) in alphabetical order.

• Bigloo by Manuel Serrano (home)

  is a Scheme system devoted to one goal: enabling Scheme based programming style where C(++) is usually required.

  Bigloo is based on a highly optimizing batch compiler (even though a simple interpreter is also included). It features a simple module system, a simple exception system, an object system, a type system, built-in lexing and parsing tools, and an extensive C FFI. It makes use of the Boehm/Weiser conservative collector for C; the FFI relies on this. Bigloo can generate very fast code. It does not completely adhere to the Scheme standard. In particular, it isn't fully tail-recursive.
• Gambit-C by Marc Feeley (home, local copy) Gambit-C includes a Scheme interpreter and an optimizing compiler which can be used to build standalone executables. The compiler produces portable C output code. It has a CL-style define-macro macro facility.
• MzScheme by Matthew Flatt and the Rice PLT group (home, local copy) is a byte-code implementation of Scheme. It features pre-emptive threads, an exception facility, a module system, a C++-like object system. It uses the Boehm/Weiser conservative garbage collector for C. MzScheme's C FFI depends on it. Also, MzScheme is the Scheme engine of MrEd which provides an extensive interface to various windowing system, and of DrScheme, a comprehensive development environment for Scheme.
• RScheme by Donovan Kolbly (home, local copy) is

  an object-oriented, extended version of the Scheme dialect of Lisp. RScheme can be compiled to C, and the C can then compiled with a normal C compiler to generate machine code. This can be done from a running system, and the resulting object code can be dynamically linked into RScheme as a program executes. By default, however, RScheme compiles to bytecodes which are interpreted by a (runtime) virtual machine.

  RScheme features a precise incremental real-time garbage collector, hygienic macros, persistence, pre-emptive threads, a Dylan-like object system, and a simple module system.
• Scheme 48 by Jonathan Rees and Richard Kelsey (web home, home, local copy) is a byte-code implementation of Scheme. It features a complete module system integrated with the interactive environment, hygienic macros, an exception system, pre-emptive threads. It has a primitive FFI and uses precise (albeit two-space-copy) garbage collection. scsh, a variant of Scheme 48, provides very powerful facilities for shell programming and a complete systems programming interface for Unix. (home, local copy) Scheme 48 also has a distributed variant Kali. Other distinguishing features are a VM implemented in Scheme (rather than C), and the structural simplicity of the system.