SWI-ProLog offers a comprehensive Free Software Prolog environment, licensed under the Lesser GNU Public License. Together with its graphics toolkit XPCE, its development started in 1987 and has been driven by the needs for real-world applications. These days SWI-Prolog is widely used in research and education as well as for commercial applications. See our download statistics. SWI-Prolog's most important features are
* Kernel licensed under the LGPL. Prolog libraries are distributed under the GPL with an additional statement that allows for use in proprietary applications. Details can be found on the license page. * fast compilation. E.g., loads 140,000 lines of code spread over 500 source-files in 2.3 seconds on an AMD 5400+ system. * Robust and free of memory leaks. In use for several servers that run 24x7 (including this web-service). * Small. The full development environment, including graphics, libraries and many interface packages requires approx. 40MB harddisk. The non-graphical kernel is about 650Kb, the graphics library adds about 1.2Mb to the image. * Scales well for large applications. No limits on program size, atom-length, term-arity or integer values. No performance degradation on predicates with many (indexed) facts. * Unbounded integer and rational number arithmetic based on GMP library. * Comprehensive set of built-in predicates, covering Part 1 of the ISO standard, the de-Facto Edinburgh Prolog standard and important parts of Quintus and SICStus Prolog. Fair compatibility to Ciao, YAP and GNU-Prolog. * Flexible and fast interface to the C- and C++-Language. The interface allows for calling both-ways, handling of non-determinism both ways and embedding of the SWI-Prolog kernel in C/C++ projects.