/usr/share/Yap/occurs.yap is in yap 5.1.3-6.
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 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 | /* $Id: occurs.yap,v 1.1 2008/02/12 17:03:52 vsc Exp $
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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 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(occurs,
[ contains_term/2, % +SubTerm, +Term
contains_var/2, % +SubTerm, +Term
free_of_term/2, % +SubTerm, +Term
free_of_var/2, % +SubTerm, +Term
occurrences_of_term/3, % +SubTerm, +Term, ?Tally
occurrences_of_var/3, % +SubTerm, +Term, ?Tally
sub_term/2, % -SubTerm, +Term
sub_var/2 % -SubTerm, +Term (SWI extra)
]).
:- use_module(library(arg),
[genarg/3]).
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
This is a SWI-Prolog implementation of the corresponding Quintus
library, based on the generalised arg/3 predicate of SWI-Prolog.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
%% contains_term(+Sub, +Term) is semidet.
%
% Succeeds if Sub is contained in Term (=, deterministically)
contains_term(X, X) :- !.
contains_term(X, Term) :-
compound(Term),
genarg(_, Term, Arg),
contains_term(X, Arg), !.
%% contains_var(+Sub, +Term) is det.
%
% Succeeds if Sub is contained in Term (==, deterministically)
contains_var(X0, X1) :-
X0 == X1, !.
contains_var(X, Term) :-
compound(Term),
genarg(_, Term, Arg),
contains_var(X, Arg), !.
%% free_of_term(+Sub, +Term)
%
% Succeeds of Sub does not unify to any subterm of Term
free_of_term(Sub, Term) :-
\+ contains_term(Sub, Term).
%% free_of_var(+Sub, +Term)
%
% Succeeds of Sub is not equal (==) to any subterm of Term
free_of_var(Sub, Term) :-
\+ contains_var(Sub, Term).
%% occurrences_of_term(+SubTerm, +Term, ?Count)
%
% Count the number of SubTerms in Term
occurrences_of_term(Sub, Term, Count) :-
count(sub_term(Sub, Term), Count).
%% occurrences_of_var(+SubTerm, +Term, ?Count)
%
% Count the number of SubTerms in Term
occurrences_of_var(Sub, Term, Count) :-
count(sub_var(Sub, Term), Count).
%% sub_term(-Sub, +Term)
%
% Generates (on backtracking) all subterms of Term.
sub_term(X, X).
sub_term(X, Term) :-
compound(Term),
genarg(_, Term, Arg),
sub_term(X, Arg).
%% sub_var(-Sub, +Term)
%
% Generates (on backtracking) all subterms (==) of Term.
sub_var(X0, X1) :-
X0 == X1.
sub_var(X, Term) :-
compound(Term),
genarg(_, Term, Arg),
sub_var(X, Arg).
/*******************************
* UTIL *
*******************************/
%% count(+Goal, -Count)
%
% Count number of times Goal succeeds.
count(Goal, Count) :-
State = count(0),
( Goal,
arg(1, State, N0),
N is N0 + 1,
nb_setarg(1, State, N),
fail
; arg(1, State, Count)
).
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