/usr/lib/swi-prolog/library/checklast.pl is in swi-prolog-nox 7.2.3+dfsg-6.
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 | /* $Id$
Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: jan@swi.psy.uva.nl
WWW: http://www.swi-prolog.org
Copyright (C): 1985-2002, University of Amsterdam
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
As a special exception, if you link this library with other files,
compiled with a Free Software compiler, to produce an executable, this
library does not by itself cause the resulting executable to be covered
by the GNU General Public License. This exception does not however
invalidate any other reasons why the executable file might be covered by
the GNU General Public License.
*/
:- module(checklast,
[ check_old_last/0
]).
:- use_module(library(lists)).
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
This module simplifies porting < 5.1.11 applications using last/2 with
the wrong argument order to >= 5.1.12. For further discussion on the
argument order of last/2, see
http://www.prolog-standard.fmg.uva.nl/twiki/bin/view/Library/PredLast2
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
check_old_last :-
print_message(informational, last_check).
user:goal_expansion(last(L,E), _) :-
print_message(warning, last_arguments(last(L,E))),
fail.
/*******************************
* CHECKING VERSION *
*******************************/
:- abolish(lists:last/2).
%% last(?List, ?Elem)
%
% Succeeds if `Last' unifies with the last element of `List'.
lists:last(List, Last) :-
\+ is_list(List), !,
print_message(error, last_call(last_call(List, Last))),
trace,
fail.
lists:last([X|Xs], Last) :-
last_(Xs, X, Last).
last_([], Last, Last).
last_([X|Xs], _, Last) :-
last_(Xs, X, Last).
/*******************************
* MESSAGES *
*******************************/
:- multifile
prolog:message/3.
prolog:message(last_check) -->
[ 'Enabled checking for wrong argument order in last/2' ].
prolog:message(last_arguments(S)) -->
{ numbervars(S, 0, _)
},
[ 'Last/2 used; check argument order: ~p'-[S] ].
prolog:message(last_call(S)) -->
[ 'Suspicious last/2 call, entering debugger: ~p'-[S] ].
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