Bigloo is an implementation of the Scheme programming language. It relies on an optimizing compiler from Scheme to C. Bigloo enables connections between Scheme code and C code. It proposes many extensions to Scheme such as a regular parser compiler, an lalr parser compiler, pattern matching, an object layer, etc.
MIT/GNU Scheme is an implementation of the Scheme programming language, providing an interpreter, compiler, source-code debugger, integrated Emacs-like editor, and a large runtime library. MIT/GNU Scheme is best suited to programming large applications with a rapid development cycle. Recent versions of the system are supported on the following platforms: GNU/Linux, *BSD, OS/2, and Windows.
Petite Chez Scheme is a freely distributable interpreted version of Chez Scheme, a high-performance implementation of ANSI Scheme with numerous extensions. Petite Chez Scheme may be used as a run-time environment for compiled Chez Scheme applications or as a stand-alone Scheme system. With the exception that the compiler is not present, Petite Chez Scheme is completely compatible with Chez Scheme.
STklos is a free Scheme System conforming to R5RS. The implementation is based on an ad-hoc Virtual Machine. It can also be compiled as a library, so that one can easily embed it in an application. Its features include an efficient and powerful object system based on CLOS, a simple-to-use module system, implementation of the full tower of numbers defined in R5RS, and easy connection to the GTK+ toolkit. STklos is the successor of STk, a Scheme interpreter tightly connected to the Tk toolkit.
Scsh is a systems-programming environment for POSIX systems and Win32, embedded in the Scheme programming language. It includes a high-level process notation for writing shell-script like programs, with pipelines and redirections. Scsh additionally provides low-level access to POSIX primitives, plus important non-POSIX extensions such as sockets. Scsh is implemented on top of Scheme48, a portable bytecode implementation of Scheme. A number of user-contributed extensions are available, including an extensible HTTP and FTP server, a socket-level PostgreSQL interface, a programmable text formatting language, and a Postscript generation language.
RScheme is an object-oriented, extended Scheme implementation with a compiler that targets C or (RScheme's own) bytecodes. It has features expected from a modern language: an object system, reflection, modules, namespaces, safe macros, threads, a system call interface (including sockets), separate compilation, and persistence, as well as the formal basis and power of the Scheme programming language. RScheme also features a powerful, elegant foreign code interface.
Chicken is a Scheme compiler that translates most of R5RS Scheme into relatively portable C. It supports fully general tail-call recursion, first-class continuations, and has a very flexible and efficient interface to C and C++. Chicken implements several extensions to the Scheme language: lightweight threads, pattern matching macros, dynamic loading of compiled code, and various object-oriented paradigms, such as TinyCLOS, and others. The library system includes hundreds of convenient modules for practical use.