swi-prolog-x 6.6.6-4 (amd64 binary) in ubuntu vivid

 SWI-Prolog is a fast and powerful ISO/Edinburgh-style Prolog compiler with a
 rich set of built-in predicates. It offers a fast, robust and small
 environment which enables substantial applications to be developed with it.
 .
 SWI-Prolog additionally offers:
 .
  * A powerful module system
  * Garbage collection
  * Unicode character set handling
  * Unbounted integer and rational number arithmetic
  * Multithreading support
  * A powerful C/C++ interface
  * GNU Readline interface
 .
 XPCE is an object-oriented symbolic programming environment for user
 interfaces. Although XPCE was designed to be language-independent, it has
 gained popularity most with Prolog.