The XLISP family

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XLISP is a family of multi-platform LISP implementations, they comprise of a Scheme compatible interpreter (bytecode compiler for versions 3 and higher) called XLISP originally written by David Betz and he added few object oriented features taken from Smalltalk to the basic Scheme language. The core runtime is written in C while the rest is implemented in XLISP itself and the program was released into the public domain until about version 2.1 where the license was changed. XLISP 2.1 is also the last version of the original XLISP package to be available in an OS/2 port.

The program was first released in 1983 as eXperimental LISP and was at the time a generic small LISP subset that was not Scheme compatible, when the first Scheme compatible version came out Mr. Betz changed the name of the package to XScheme but changed it back to XLISP after a couple of years. Various versions of the package are used in open source projects externally or internally as scripting engines, it is also the basis for the LISP that is used as an internal scripting engine by AutoCAD (AutoLISP) and some compatible packages like IntelliCAD.


    • WINTERP is a derivative of XLISP-PLUS 2.1 that adds widget support for UNIX like operating systems that have the Motif widget library installed.
  • Vienna LISP, also known as VLISP is an XLISP fork that is Common LISP compatible and adds a bytecode compiler, note that Vienna LISP is preferred usage over VLISP since there are at the least five other projects that use the VLISP moniker.
  • Nyquist is a music programming language based on XLISP.
  • S-Lisp bolts s 3D graphics library onto XLISP. An Image Algebra or ANIMAL was an experimental version that handled image processing.


  • 0.0 (Jan 1983)
  • 1.0 (Mar 1983)
  • 1.1 (Jun 1983)
  • 1.2 (Oct 1984)
  • 1.4 (Jan 1985)
  • 1.6 (Jan 1986)
  • 1.7 (Jun 1986)
  • 2.0 (Feb 1988)
  • 2.1 (1991)
  • XLISP v3 (1997 - some trivial bug fixes in 1998 and 2002)
Only released in a version for Microsoft Windows, introduces a bytecode compiler.
  • WINTERP 2.10 (2008) - Last known version.
Note that WINTERP release numbers are not synchronised with XLISP-PLUS, the 2.1 release is similar to a XP version 3.04 rather than the classic XP 2.1.


Articles & papers
  • R. Brunelli; C. M. Modena: ANIMAL: An Image Algebra - An image processing environment based on XLISP - 1989 [1]

Licence and availability


  • David Betz - Original Xlisp author


Code examples
  • VEOS - An old experimental distributed system written in XLISP
  • VMAKE - A software configuration management tool written in Vienna LISP.