/usr/lib/swi-prolog/boot/bags.pl is in swi-prolog-nox 6.6.6-5.
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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 | /* $Id$
Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@cs.vu.nl
WWW: http://www.swi-prolog.org
Copyright (C): 1985-2010, University of Amsterdam,
VU University 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 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('$bags',
[ findall/3, % +Templ, :Goal, -List
findall/4, % +Templ, :Goal, -List, +Tail
bagof/3, % +Templ, :Goal, -List
setof/3 % +Templ, :Goal, -List
]).
:- meta_predicate
findall(?, 0, -),
findall(?, 0, -, ?),
bagof(?, ^, -),
setof(?, ^, -).
:- noprofile((
findall/4,
findall/3,
bagof/3,
setof/3,
findall_loop/4)).
:- '$iso'((findall/3,
bagof/3,
setof/3)).
%% findall(-Var, +Goal, -Bag) is det.
%% findall(-Var, +Goal, -Bag, +Tail) is det.
%
% Bag holds all alternatives for Var in Goal. Bag might hold
% duplicates. Equivalent to bagof, using the existence operator
% (^) on all free variables of Goal. Succeeds with Bag = [] if
% Goal fails immediately.
%
% The findall/4 variation is a difference-list version of
% findall/3.
findall(Templ, Goal, List) :-
findall(Templ, Goal, List, []).
findall(Templ, Goal, List, Tail) :-
setup_call_cleanup(
'$new_findall_bag',
findall_loop(Templ, Goal, List, Tail),
'$destroy_findall_bag').
findall_loop(Templ, Goal, List, Tail) :-
( Goal,
'$add_findall_bag'(Templ) % fails
; '$collect_findall_bag'(List, Tail)
).
%% bagof(+Var, +Goal, -Bag) is semidet.
%
% Implements Clocksin and Melish's bagof/3 predicate. Bag is
% unified with the alternatives of Var in Goal, Free variables of
% Goal are bound, unless asked not to with the existential
% quantifier operator (^).
bagof(Templ, Goal0, List) :-
'$free_variable_set'(Templ^Goal0, Goal, Vars),
( Vars == v
-> findall(Templ, Goal, List),
List \== []
; findall(Vars-Templ, Goal, Answers),
bind_bagof_keys(Answers,_),
keysort(Answers, Sorted),
pick(Sorted, Vars, List)
).
bind_bagof_keys([], _).
bind_bagof_keys([W-_|WTs], Vars) :-
term_variables(W, Vars, _),
bind_bagof_keys(WTs, Vars).
pick(Bags, Vars1, Bag1) :-
pick_first(Bags, Vars0, Bag0, RestBags),
select_bag(RestBags, Vars0, Bag0, Vars1, Bag1).
select_bag([], Vars0, Bag0, Vars1, Bag1) :- !, % last one: deterministic
Vars0 = Vars1,
Bag0 = Bag1.
select_bag(_, Vars, Bag, Vars, Bag).
select_bag(RestBags, _, _, Vars1, Bag1) :-
pick(RestBags, Vars1, Bag1).
%% pick_first(+Bags, +Vars, -Bag1, -RestBags) is semidet.
%
% Pick the first result-bag from the list of Templ-Answer. Note
% that we pick all elements that are equal under =@=, but because
% the variables in the witness are canonized this is the same as ==.
%
% @param Bags List of Templ-Answer
% @param Vars Initial Templ (for rebinding variables)
% @param Bag1 First bag of results
% @param RestBags Remaining Templ-Answer
pick_first([Vars-Templ|T0], Vars, [Templ|T], RestBag) :-
pick_same(T0, Vars, T, RestBag).
pick_same([V-H|T0], Vars, [H|T], Bag) :-
V == Vars, !,
pick_same(T0, Vars, T, Bag).
pick_same(Bag, _, [], Bag).
%% setof(+Var, +Goal, -Set) is semidet.
%
% Equivalent to bagof/3, but sorts the resulting bag and removes
% duplicate answers. We sort immediately after the findall/3,
% removing duplicate Templ-Answer pairs early.
setof(Templ, Goal0, List) :-
'$free_variable_set'(Templ^Goal0, Goal, Vars),
( Vars == v
-> findall(Templ, Goal, Answers),
Answers \== [],
sort(Answers, List)
; findall(Vars-Templ, Goal, Answers),
( ground(Answers)
-> sort(Answers,Sorted),
pick(Sorted,Vars,List)
; bind_bagof_keys(Answers,_VDict),
sort(Answers, Sorted),
pick(Sorted, Vars, Listu),
sort(Listu,List) % Listu ordering may be nixed by Vars
)
).
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