OpenLisp running inside Emacs
ParadigmsMulti-paradigm: functional, procedural, object-oriented, reflective, meta
Designed byChristian Jullien
DeveloperChristian Jullien
First appearedApril 1988; 35 years ago (1988-04)
Stable release
11.7.0 / 13 December 2022; 13 months ago (2022-12-13)
Typing disciplineDynamic, strong
Implementation languageC, OpenLisp
Platformx86, x86-64, IA-64, SPARC, PowerPC, MIPS, Alpha, PA-RISC, ARM, AArch64, RISC-V, Loongson
OSWindows, most Unix-based, Linux, macOS, FreeBSD, OpenBSD, NetBSD, Solaris, HP-UX, AIX, QNX, DOS, OS/2, Pocket PC, OpenVMS, z/OS, Cygwin
Influenced by

OpenLisp is a programming language in the Lisp family developed by Christian Jullien[1] from Eligis. It conforms[2][3][4] to the international standard for ISLISP published jointly by the International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC), ISO/IEC 13816:1997(E),[5][6] revised to ISO/IEC 13816:2007(E).[7]

Written in the programming languages C and Lisp, it runs on most common operating systems. OpenLisp is designated an ISLISP implementation, but also contains many Common Lisp-compatible extensions (hashtable, readtable, package, defstruct, sequences, rational numbers) and other libraries (network socket, regular expression, XML, Portable Operating System Interface (POSIX), SQL, Lightweight Directory Access Protocol (LDAP)).[8]

OpenLisp includes an interpreter associated to a read–eval–print loop (REPL), a Lisp Assembly Program (LAP) and a backend compiler for the language C.


The main goal of this Lisp version is to implement a fully compliant ISLISP system (when launched with --islisp flag, it is strictly restricted to ISO/IEC 13816:2007(E) specification). The secondary goal is to provide a complete embeddable Lisp system linkable to C/C++ or Java (via Java Native Interface (JNI)). A callback mechanism is used to communicate with the external program. Other goals are to be usable as scripting language or glue language and to produce standalone program executables.


Despite its name, OpenLisp is proprietary software. Its interpreter is available free of charge for any noncommercial use.

User interface

OpenLisp mainly runs in console mode: cmd.exe on Microsoft Windows, and terminal emulator on Unix-based systems.

 ;; OpenLisp v11.x.y (Build: XXXX) by C. Jullien [Jan 01 20xx - 10:49:13]
 ;; Copyright (c) Eligis - 1988-20xx.
 ;; System 'sysname' (64-bit, 8 CPU) on 'hostname', ASCII.
 ;; God thank you, OpenLisp is back again!
 ? (fib 20)
 ;; elapsed time = 0.003s, (0 gc).
 = 6765
 ? _

Alternate solutions include running OpenLisp from Emacs via setting up Emacs inferior-lisp-mode, or using an integrated development environment (IDE) which supports OpenLisp syntax. LispIDE by DaanSystems does so natively.


Memory manager

Internally, OpenLisp uses virtual memory to allocate and extend objects automatically. Small objects of the same type are allocated using a Bibop (BIg Bag Of Pages) memory organization. Large objects use a proxy which point to the real object in Lisp heap. The conservative garbage collection is a mark and sweep with coalescing heap (sweep phase can be configured to use threads).

Data types

OpenLisp uses tagged architecture (4 bits tag on 32-bit, 5 bits tag on 64-bit) for fast type checking (small integer, float, symbol, cons, string, vector). Small integers (28 bits on 32-bit, 59 bits on 64-bit) are unboxed, large (32/64-bit) integers are boxed. As required by ISLISP, arbitrary-precision arithmetic (bignums) are also implemented. Characters (hence strings) are either 8-bit (ANSI, EBCDIC) or 16/32-bit if Unicode support is enabled.

Evaluator and compiler

The Lisp Kernel, native interpreter and basic libraries are hand coded in the language C, LAP intermediate language produced by the compiler is then translated to C by the C backend code generator.


In 1988, the very first motive behind OpenLisp was to implement a Lisp subset to extend EmACT, an Emacs clone. ISLISP became an obvious choice quickly. Further development ensued.

OpenLisp milestones[9]
Year Version Main feature
1988 1.0 OpenLisp begun as a toy language named MLisp (Minimal Lisp) to experiment with ideas from ISLISP standards process
1993 3.3 First port on 64-bit machine (DEC Alpha OSF/1); name change from MLisp to OpenLisp
1994 4.0 First commercial use
1995 4.5 Socket streams support
1997 5.7 OpenLisp is first Lisp to implement ISLISP ISO/IEC 13816:1997(E) standard.[10]
1998 5.8 Unicode optional support
2000 6.6 Lisp to LAP compiler; LAP is interpreted by a virtual machine embedded in OpenLisp; speed improved about 2x
2003 7.5 Lisp to C backend; able to compile an application with many Lisp files to a standalone executable; speed improved from 10x to 20x
2007 8.7 Changes to match ISO/IEC 13816:2007(E) revision[7]
2010 9.2 Native integer arbitrary-precision arithmetic support
2021 11.2 Added complete CLtL format extension; improve heap detection
2022 11.4 Rework of activation blocks makes interpreter around 15% faster. Experimental ASDF clone.
2022 11.5 Generic function calls are ~3x faster. Improved regex internal module.
2022 11.6 Add <simple-bit-vector> type and related BIT functions similar to CLtL equivalent.
2022 11.7 Current version
1958 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020
 LISP 1, 1.5, LISP 2(abandoned)
 Lisp Machine Lisp
 Scheme  R5RS  R6RS  R7RS small
 ZIL (Zork Implementation Language)
 Franz Lisp
 Common Lisp  ANSI standard
 Le Lisp
 MIT Scheme
 Chez Scheme
 Emacs Lisp
 PLT Scheme  Racket
 GNU Guile
 Visual LISP


OpenLisp claims to be extremely portable, it runs on many operating systems including: Windows, most Unix and POSIX based (Linux, macOS, FreeBSD, OpenBSD, NetBSD, Solaris, HP-UX, AIX, Cygwin, QNX), DOS, OS/2, Pocket PC, OpenVMS, z/OS. The official website download section contains over 50 different versions.

Standard libraries


OpenLisp can interact with modules written in C using foreign function interface (FFI), ISLISP streams are extended to support network socket (./net directory includes samples for Hypertext Transfer Protocol (http), JavaScript Object Notation (JSON), Post Office Protocol 3 (POP3), Simple Mail Transfer Protocol (SMTP), Telnet, Rss), a simplified Extensible Markup Language (XML) reader can convert XML to Lisp. A basic SQL module can be used with MySQL, Odbc, SQLite, PostgreSQL. A comma-separated values (CSV) module can read and write CSV files.


Developer tools include data logging, pretty-printer, profiler, design by contract programming, and unit tests.


Some well known algorithms are available in ./contrib directory (Dantzig's simplex algorithm, Dijkstra's algorithm, Ford–Fulkerson algorithm). Modules are shipped using BSD licenses.

Origin of name

The prefix Open refers to open systems not to the open-source model.[11]

The name was chosen in 1993 to replace the MLisp internal code name which was already used by Gosling Emacs (as successor of Mocklisp).

OpenLisp programming language is different than OpenLISP, a project begun in 1997 to implement Locator/Identifier Separation Protocol.


This section describes how a compiler transforms Lisp code to C.

Source code

The Fibonacci number function (this classic definition used in most benchmarks is not the most efficient way to compute fib)

(defun fib (n)
   (cond ((eq n 1) 1)
         ((eq n 2) 1)
         (t (+ (fib (- n 1)) (fib (- n 2))))))

LAP intermediate code

Lisp compiler translates Lisp source code to the following intermediate code. It is followed by a peephole optimization pass that uses this intermediate format to analyze and optimize instructions. After optimization, final LAP code is:

  ((fentry fib 1 0 0)
   (param 0)
   (jeq _l004 '1)
   (jneq _l003 '2)
   (move a1 '1)
   (gsub1 a1)
   (recurse 1)
   (move a2 a1)
   (param 0)
   (gsub a1 '2)
   (recurse 1)
   (gadd a2 a1)

C code translation

Finally, C code generator uses LAP code to translate instructions in C.

static POINTER 
OLDEFCOMPILED1(olfib_00, p1) {
        POINTER a1;

        a1 = p1;
        if (eq(a1, olmakefix(1))) goto _l004;
        if (!eq(a1, olmakefix(2))) goto _l003;
        return olmakefix(1);
        a1 = ollapgsub(a1, olmakefix(1));
        a2 = olfib_00(a1);
        a1 = ollapgsub(p1, olmakefix(2));
        a1 = olfib_00(a1);
        a1 = ollapgadd(a2, a1);
        return a1;

Style guide

Line length

OpenLisp accepts lines having unlimited length. The recommended style is that each line of text in code should have at most 80 characters per line.


It has been chosen by SDF Public Access Unix System nonprofit public access Unix systems on the Internet[12][13] as one of its programming languages available online.

Bricsys uses OpenLisp to implement AutoLISP in its Bricscad computer-aided design (CAD) system.[14]

MEVA [15] is entirely written with OpenLisp.

Università degli Studi di Palermo uses OpenLisp to teach Lisp.[16]


  1. ^ Parquier, Pierre (2000). "JTC1/SC22 N3170". ISO/IEC. Retrieved 11 March 2012.[permanent dead link]
  2. ^ Simonsen, Keld (13 March 1999). "Islisp – faq". ISO/IEC. Retrieved 11 November 2016.
  3. ^ Nobuto, Izumi (Tohoku Univ., Grad. Sch.); Takayasu, Ito (Tohoku Univ., Grad. Sch.) (1999). "Interpreter and Compiler of the ISO Standard Lisp ISLISP". Transactions- Information Processing Society of Japan. Transactions of Information Processing Society of Japan. ISSN 0387-5806. Archived from the original on 26 August 2018. Retrieved 17 June 2013.((cite journal)): CS1 maint: multiple names: authors list (link)
  4. ^ McJones, Paul (2010). "ISLISP". Software Preservation Group. Retrieved 18 March 2012.
  5. ^ "ISO/IEC 13816:1997(E)". International Organization for Standardization. Retrieved 11 November 2018.
  6. ^ Parquier, Pierre (JTC1 SC22 WG16 Convenor) (1996). "ISO/IEC JTC1 SC22 WG16 N177 – DIS vote". ISO/IEC. Retrieved 15 March 2012.((cite web)): CS1 maint: numeric names: authors list (link)
  7. ^ a b "ISO/IEC 13816:2007(E)". International Organization for Standardization. Retrieved 11 November 2018.
  8. ^ Jullien, Christian (2011). "OpenLisp v9.8.0 Reference Manual". Eligis. Retrieved 14 March 2012.
  9. ^ Jullien, Christian (2011). "OpenLisp ChangeLog". Eligis. Retrieved 15 March 2012.
  10. ^ Rinehuls, William (4 August 1999). "JTC1/SC22 N2969". ISO/IEC. Retrieved 11 November 2016.
  11. ^ Jullien, Christian (2011). "OpenLisp FAQ". Eligis. Retrieved 15 March 2012.
  12. ^ Stover, Gene Michael (2005). "7.2 Languages on SDF". SDF Public Access Unix System, Inc. Retrieved 14 March 2012.
  13. ^ "Hosting companies". ALU (Association of Lisp Users). Archived from the original on 9 February 2011. Retrieved 18 March 2012.
  14. ^ "Bricscad News". Bricscad. 2009. Retrieved 20 March 2012.
  15. ^ "Competitive Intelligence and Decision Problems". Amos Davis. 2013. Retrieved 30 September 2014.
  16. ^ "Corso di Informatica Teorica". Università degli Studi di Palermo. 2013. Retrieved 22 March 2013.