Stalin
- A powerful optimizing Scheme compiler from Jeffery Mark Siskind at the NEC Research Institute. Sacrifices functions such as call/cc in favor of efficiency, but generated code is remarkably bulletproof and fast.
- http://www.cis.upenn.edu/~screamer-tools/home.html

Scsh FAQ
- The FAQ for Scsh, the Scheme Shell.
- http://www.alphanet.ch/~schinz/scsh-faq/scsh-faq_toc.html

Schoca (Scheme for OCaml)
- An implementation of the Scheme language in OCaml. The primary purpose of Schoca is the use as an embedded extension language in OCaml applications. [Open source, GPL]
- http://sf.net/projects/chesslib

Pseudoscheme
- Embeds Scheme in Common Lisp.
- http://mumble.net/~jar/pseudoscheme/

Oaklisp
- Object-oriented Scheme dialect with first-class types, multiple inheritance, lexically distributed method definitions. based on bytecode emulator, yet reasonably fast. Description, downloads, bibliography. [Open Source, GPL]
- http://www.bcl.hamilton.ie/~bap/oaklisp/

EuScheme Sources
- Small implementation of Level 0 EuLisp, downloads in formats: tar, tgz, zip.
- http://people.bath.ac.uk/masrjb/Sources/

WinScm
- Scheme environment for Windows 3.1/95; interpreter independent, though defaults to Jaffer's SCM. Used at University of Lille 1, France, for introductory programming course. Free downloads. English, Française.
- http://www2.lifl.fr/~routier/enseignement/winscm/winscmeng.html

LEGOScheme
- Lego/Scheme compiler for Lego MindStorms Robot kits, alternative to Visual Basic. Description, documents, downloads.
- http://www.indiana.edu/~legobots/legoscheme/

PC Scheme
- Texas Instruments system for DOS OS; no longer maintained; download formats: source, executable/binary.
- ftp://swiss-ftp.ai.mit.edu/pub/pc-scheme/

Pico
- Tiny, expressive; made to teach advanced computer science ideas to non-computer science students; mixes power of languages like Scheme, with standard infix notation known from calculus. Has: garbage collected tables (arrays), higher order functions, objec
- http://pico.vub.ac.be/

CMU AI Repository Free/Shareware Scheme Implementations
- Yet more Scheme implementations from the CMU AI Repository. Many of these are also available from the Indiana University Scheme Repository.
- http://www.cs.cmu.edu/afs/cs/project/ai-repository/ai/lang/scheme/impl/0.html

STklos
- Derived from STkn implementation based on an ad-hoc virtual machine, byte compiler; compilable as library to embed in other programs, has object system with MOP, multiple inheritance, generic functions, multimethods, module system, full R5RS tower of numb
- http://www.stklos.org/

STk
- R4RS Scheme interpreter with interface to access Tk graphical package; can be seen as a standard Tk package with Tcl replaced by a Scheme interpreter. Has efficient CLOS-like object-oriented system, STklos.
- http://kaolin.unice.fr/STk/

An Executable Denotational Semantics for Scheme
- SchemeDS, as defined in R5RS. Program coded in R5RS Scheme. Description, documents, downloads. [AppSolutions Software Licensing]
- http://www.appsolutions.com/SchemeDS/

Elk Scheme: The Extension Language Kit
- New site. Embeddable, reusable extension language subsystem for programs coded in C/C++, also a useful standalone Scheme implementation with interfaces to POSIX, Unix, X11.
- http://sam.zoy.org/elk/

Elk: Scheme-based Extension Language Kit
- Old site, last update 1997. Embeddable, reusable extension language subsystem for applications written in C/C++, also a useful standalone Scheme implementation with interfaces to POSIX, Unix, X11.
- http://www-rn.informatik.uni-bremen.de/software/elk/

Chez Scheme
- Reliable, high performance implementation, by Cadence Research Systems. Free version exists. [Commercial]
- http://www.scheme.com/

T History
- Fairly detailed, by Olin Shivers.
- http://www.paulgraham.com/thist.html

T Revival Project
- Scheme dialect and implementation, incompatible with R5RS, but an R3RS compatibility layer exists; to grow more compatible with R5RS over time. Description, manual, downloads, mail list, IRC, contacts, plans.
- http://mumble.net/~campbell/t/t.html

T Project
- History with: downloads, contributors, timeline, publications, influence, users, successors, Olin history errata. By Jonathan A. Rees.
- http://mumble.net/~jar/tproject/

Scheme 48
- Jonathan A. Rees's unofficial page: history, links, status.
- http://mumble.net/~jar/s48/

XLisp-Stat
- Based on XLisp, but with built-in statistics support.
- http://www.stat.uiowa.edu/~luke/xls/xlsinfo/node1.html

XLisp-Plus
- Lisp version based on, and evolutionary improvement on, experimental XLisp.
- http://www.almy.us/xlisp.html

Sketchy
- Interpreter for pure functional applicative Scheme dialect, a variant of pure LISP plus global definitions (define), first-class continuations (call/cc), input/output functions (read, write, ...). Downloads: source, binaries. Sells: tutorial, reference ma
- http://www.t3x.org/sketchy/

Unlikely Scheme
- Small, standard-complying implementation, in C++. [Open source, zlib license]
- http://marijn.haverbeke.nl/unlikely/

Petite Chez Scheme
- A complete Scheme system that is fully compatible with Chez Scheme but uses high-speed threaded interpreter technology in place of Chez Scheme's incremental native-code compiler. [Freeware]
- http://www.scheme.com/petitechezscheme.html

Kali Scheme
- A distributed implementation of Scheme that permits efficient transmission of higher-order objects such as closures and continuations.
- http://community.schemewiki.org/kali-scheme/

Gauche
- An R5RS Scheme implementation developed to be a handy script interpreter. Quick startup, built-in system interface, native multilingual support. [Open source, BSD license]
- http://www.shiro.dreamhost.com/scheme/gauche/

Chicken
- A Scheme compiler which compiles a subset of R5RS into C. Uses the ideas presented in Baker's paper "Cheney on the MTA". It is highly portable, reasonably efficient and makes interfacing to C and C++ very easy.
- http://www.call-with-current-continuation.org

Narsi
- Portable scheme interpreter by Britt Park. Other free software: Cdoc, simple program to generate pretty TeX output from annotated C/C++ code. Userblock, simple user space block device driver kit for Linux. UVFS, user space filesystem kit.
- http://www.sciencething.org/geekthings/

Sizzle
- A Scheme interpreter implemented as a library which can be embedded into C programs, as well as a standalone interpreter. Mostly R5RS, Guile compatible, and includes regular expressions and most Posix functions.
- http://uebb.cs.tu-berlin.de/~magr/sizzle/sizzle.en.html

Better Scheme
- Language designed and largely implemented, now a matter of coding, documenting. Goals: high consistency; improve language's functional nature; consistency with lambda calculus; optimize, but not at cost of other goals.
- http://www.cs.oberlin.edu/~jwalker/bscheme/

Bigloo
- System with one goal: enable Scheme programming style where C(++) is usually needed; makes Scheme practical via features found in most normal languages but not Scheme and functional programming. Generators for C code, Java Virtual Machine, .NET bytecode.
- http://www-sop.inria.fr/mimosa/fp/Bigloo/

PLT Scheme
- Advocacy and authoring group, umbrella name for family of implementations: DrScheme (Scheme, MzScheme, MrEd); books: How to Design Programs, How to Use Scheme; and TeachScheme! project. University-based, supported by many volunteers writing code, document
- http://www.plt-scheme.org/

MzScheme
- Small, embeddable, scripting PLT Scheme implementation: R5RS compliant, full numerical tower, threads (all platforms), exceptions, modules, class-based objects, regular-expression matching, TCP/IP. For Macintosh, Unix, Windows 32-bit.
- http://www.plt-scheme.org/software/mzscheme/

Inlab Scheme
- A commercial Scheme which is freely available for non-commercial use on Linux and FreeBSD. It has support for several features like bitmap/greymap processing and can be used as a general tool for image processing, OCR or specialized optical object and pa
- http://www.inlab.de/scheme/

Pocket Scheme
- For MIPS, SH3, ARM-based Windows CE devices. Supports Aubrey Jaffer's SLIB, has initialization file for same, parenthesis-balancing text editor. Windows NT version exists. [Open Source, Artistic License]
- http://www.mazama.net/scheme/pscheme.htm

DrScheme
- Full Scheme programming environment for Macintosh, many Unixes, Windows. Has module and object systems, platform-independent graphics. Ideal for beginners; one of the major design goals is a flexible teaching environment.
- http://www.drscheme.org/

Infer Project
- Statically-typed Scheme dialect, written in Infer, combines many of the best features of Scheme and ML. NSF funded.
- http://www.cs.indiana.edu/~chaynes/infer.html

Vx-scheme
- A compact (<64 Kb) implementation of R4RS Scheme that compiles for VxWorks/Tornado (and is integrated with the system symbol table). [Open source, Artistic License]
- http://colin-smith.net/vx-scheme/

Scsh
- Scheme Shell, broad-spectrum system programming environment for Unix, embedded in R5RS Scheme 48. Supports concurrent system programming, sophisticated I/O and automatic garbage collection for process resources.
- http://www.scsh.net/

TinyScheme
- Based on Mini-Scheme, tiny implementation, almost a full R5RS Scheme. Goal: embedded scripting use, but works as standalone interpreter and extensible shell tool. Recent changes reduced executable size to about 64KB on Linux/x86. [BSD]
- http://tinyscheme.sourceforge.net/

SIOD: Scheme in One Defun
- Very small, portable implementation, has some database, Unix programming, CGI scripting extensions. Runs on DOS, Linux, Unix, Windows. Free source downloads.
- http://people.delphiforums.com/gjc/siod.html

The Ksi Scheme Interpreter
- Ksi is a portable, embeddable Scheme implementation written in C. Unfortunately its documentation is all in Russian at this point.
- http://ksi.sourceforge.net/

EdScheme
- Interpreter for Macintosh or Windows. Has "friendly and convenient interactive programming environment" with language sensitive editor, full documentation. [commercial, free 14 day download]
- http://www.schemers.com/edschem.html

3DScheme
- Two systems for Windows with built in "industrial-strength" solid modeler based on the ACIS solid modeler Geometric Modeling Kernel.
- http://www.schemers.com/3dscm1.html

Scheme 48 User's Guide
- HTMLized by Margaret Fleck, one of the authors of Envision.
- http://www.cs.hmc.edu/~fleck/envision/scheme48/user-guide.html

Scheme Implementations and Mailing Lists
- A list of Scheme implementations from the Scheme FAQ maintained by Mark Kantrowitz.
- ftp://ftp.cs.indiana.edu/pub/scheme-repository/doc/misc/scheme_2.faq

T
- Scheme-like language developed at Yale; is to Scheme rather as NIL is to Lisp; mainly of interest to historians and theoreticians. FTP for v3.1.
- ftp://ftp.cs.indiana.edu/pub/scheme-repository/imp/t/

Indiana University Scheme Repository: Implementations
- Even more Scheme implementations freely available from the Indiana U. repository.
- http://www.cs.indiana.edu/scheme-repository/imp.html

LispMe
- Newer versions here. Scheme system for the Palm Pilot PDA developed by Fred Bayer.
- http://www.lispme.de/lispme/index.html

SXM, CXEMA
- Portable Scheme implementation, conforms to IEEE/ANSI standard, supports all features of R5RS Report, many features of Chez Scheme and various SRFIs. Derived from XScheme: object system dropped, many changes, additions.
- http://www.malgil.com/sxm/

QScheme
- A fast, small Scheme interpreter which is mostly compliant with the R5RS standard.
- http://www.sof.ch/dan/qscheme/index-e.html

KSM-Scheme
- A R5RS Scheme interpreter which integrates with C, allowing calling of C functions and accessing C variables from Scheme. It provides a mechanism to load C shared libraries. It runs on x86 and PowerPC based Linux systems.
- http://square.umin.ac.jp/~hchang/ksm/

Larceny Project
- Simple, efficient Scheme run-time system, for SPARC architecture. Petit Larceny is portable and emits C, for Linux (Intel IA32), Macintosh OS X (PowerPC), Solaris (SPARC), Windows. Common Larceny runs on Microsoft Common Language Runtime (CLR), emits MS
- http://www.ccs.neu.edu/home/will/Larceny/

MIT Scheme
- From MIT, for many systems, has comprehensive code library, includes most functionality of ANSI Standard Common Lisp (CLtL2), many low-level OS interactions. Distributed with system is LIAR (LIAR Imitates Apply Recursively), optimizing compiler that outpu
- http://www.swiss.ai.mit.edu/projects/scheme/

XLISP
- A superset of the Scheme dialect of Lisp with extensions to support object-oriented programming.
- http://www.mv.com/ipusers/xlisper/

Galapagos
- An interactive multithreaded Scheme interpreter with turtle graphics for Windows 95, based on SCM.
- http://www.cs.bgu.ac.il/~elad/GALAPAGOS/

Gambit
- A portable, high-performance implementation of Scheme based on an optimizing compiler by Marc Feeley. Developed at University of Montreal.
- http://www.iro.umontreal.ca/~gambit/

SCM
- A portable Scheme implementation written by Aubrey Jaffer.
- http://www-swiss.ai.mit.edu/~jaffer/SCM.html

VSCM
- A portable Scheme implementation written by Matthias Blume of Princeton University. No longer actively developed.
- http://www.cs.princeton.edu/~blume/vscm/

RScheme
- Portable, extended Scheme with reflective object(-oriented) system, operating system services, modules, threads, many system programming features (integrates with, compiles to C or bytecodes) and useful extensions. [Open Source]
- http://www.rscheme.org/