/usr/lib/swi-prolog/library/gensym.pl is in swi-prolog-nox 7.6.4+dfsg-1build1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 | /* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 1985-2013, University of Amsterdam
VU University Amsterdam
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
*/
:- module(gensym,
[ reset_gensym/0,
reset_gensym/1, % +Base
gensym/2 % +Base, -Symbol
]).
:- set_prolog_flag(generate_debug_info, false).
/** <module> Generate unique symbols
The predicate gensym/2 is a traditional predicate to generate unique
symbols. It should be used with care.
*/
%! gensym(+Base, -Unique)
%
% Generate <Base>1, <Base>2, etc atoms on each subsequent call.
% Note that there is nothing that prevents other parts of the
% application to `invent' the same identifier. The predicate
% gensym/2 is thread-safe in the sense that two threads generating
% identifiers from the same Base will never generate the same
% identifier.
%
% @see uuid/1, term_hash/2, variant_sha1/2 may be used to
% generate various unique or content-based identifiers
% safely.
gensym(Base, Atom) :-
atom_concat('$gs_', Base, Key),
flag(Key, Old, Old+1),
record_gensym(Key, Old),
New is Old+1,
atom_concat(Base, New, Atom).
record_gensym(Key, 0) :-
!,
recordz('$gensym', Key).
record_gensym(_, _).
%! reset_gensym
%
% Reset all gensym counters. Please beware this is dangerous: gensym
% may be in use by other modules that do not expect their counter to
% be reset!
reset_gensym :-
with_mutex('$gensym', do_reset_gensym).
do_reset_gensym :-
( recorded('$gensym', Key, Ref),
erase(Ref),
set_flag(Key, 0),
fail
; true
).
%! reset_gensym(+Base)
%
% Reset a specific gensym counter. Please beware this still is
% dangerous as other code may use gensym with the same atom!
reset_gensym(Base) :-
atom_concat('$gs_', Base, Key),
set_flag(Key, 0).
:- multifile sandbox:safe_primitive/1.
sandbox:safe_primitive(gensym:gensym(_,_)).
|