dev-lang/gprolog
Native Prolog compiler with constraint solving over finite domains (FD)
USE Flags
debug
Global: Enable extra debug codepaths, like asserts and extra output. If you want to get meaningful backtraces see http://www.gentoo.org/proj/en/qa/backtraces.xml
doc
Global: Adds extra documentation (API, Javadoc, etc)
examples
Global: Install examples, usually source code