A practical lambda-calculator is a normal-order evaluator for the untyped lambda-calculus, extended with convenient commands and shortcuts to make programming in it more productive. Shortcuts are distinguished constants that represent terms. Commands define new shortcuts, activate tracing of all reductions, compare terms modulo alpha-conversion, print all defined shortcuts and evaluation flags, etc. Terms to evaluate and commands are entered at a read-eval-print-loop (REPL) "prompt" or "included" from a file by a special command. A Haskell branch is an embedding of the lambda calculator (as a domain-specific language) into Haskell. The calculator can be used interactively within Hugs or GHCi.
jMax is a visual programming environment for building interactive real-time musical and multimedia applications by allowing the user to interactively design dataflow circuits. The basic data types that can go through are integers, symbols, lists, etc. It is an event-driven system and has been used for MIDI processing. A second part of the system (DSP) allows a continuous signal to flow through a circuit, which is most useful for PCM sound (ie. microphone, sound files, etc.). The system is extensible by using shared libraries, you may add data processor types, data types, GUI elements, device types, and more. Data processors may also be designed as circuits and reused.
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.
guile spread is a guile module that conveniently wraps the Spread C libraries provided with the Spread 3.15.2 distribution. Spread is a local/wide area group communication toolkit that runs on most modern operating systems. It allows convenient mechanisms for reliable multicasting information between applications as well as providing many more complicated assurances.