$ qpkg -nc -i -vv gprolog
dev-lang/gprolog-1.2.13
   /usr/portage/dev-lang/gprolog/gprolog-1.2.13.ebuild
        GNU Prolog is a native Prolog compiler with constraint solving over finite domains (FD) [ http://www.gnu.org ]
dev-lang/gprolog-1.2.16
   /usr/portage/dev-lang/gprolog/gprolog-1.2.16.ebuild
        GNU Prolog is a native Prolog compiler with constraint solving over finite domains (FD) [ http://pauillac.inria.fr/~diaz/gnu-prolog/ ]

$ emerge search gprolog

Searching...   
[ Results for search key : gprolog ]
[ Applications found : 1 ]
 
*  dev-lang/gprolog
      Latest version available: 1.2.16
      Latest version installed: [ Not Installed ]
      Size of downloaded files: 2,420 kB
      Homepage:    http://pauillac.inria.fr/~diaz/gnu-prolog/
      Description: GNU Prolog is a native Prolog compiler with constraint solving over finite domains (FD)
      License:     GPL-2



$ apt-cache search gprolog
gprolog - GNU Prolog compiler
gprolog-doc - Documentation for the GNU Prolog compiler

$ apt-cache show gprolog
Package: gprolog
Priority: optional
Section: devel
Installed-Size: 3664
Maintainer: Salvador Abreu <spa@debian.org>
Architecture: i386
Version: 1.2.18-12
Depends: libc6 (>= 2.3.2.ds1-4), gcc (>= 3.3)
Recommends: gprolog-doc
Filename: pool/main/g/gprolog/gprolog_1.2.18-12_i386.deb
Size: 1239542
MD5sum: 9a5aae56d8909693bbbd3f49c2b2a9e4
Description: GNU Prolog compiler
 GNU Prolog is a free Prolog compiler with constraint solving over finite
 domains (FD) developed at INRIA by Daniel Diaz.  GNU Prolog is based on two
 systems developed by the same author (with lot of code rewriting and a lot of
 new extensions): wamcc and clp(FD).  Much work has been devoted to make it
 ISO compatible, full compliance being one of its goals.
 .
 This package contains the compiler and runtime system for the ISO
 standard version of GNU Prolog.