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/* Part of SWI-Prolog
Author: Jan Wielemaker
E-mail: J.Wielemaker@vu.nl
WWW: http://www.swi-prolog.org
Copyright (c) 1985-2014, 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.
*/
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Copyright notes: findall/3, bagof/3 and setof/3 are part of the standard
folklore of Prolog. The core is findall/3 based on C code that was
written for SWI-Prolog. Older versions also used C-based implementations
of bagof/3 and setof/3. As these proved wrong, the current
implementation is modelled after an older version of Yap. Ulrich
Neumerkel fixed the variable preservation of bagof/3 and setof/3 using
an algorithm also found in Yap 6.3, where it is claimed: "uses the
SICStus algorithm to guarantee that variables will have the same names".
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
:- module('$bags',
[ findall/3, % +Templ, :Goal, -List
findall/4, % +Templ, :Goal, -List, +Tail
findnsols/4, % +Count, +Templ, :Goal, -List
findnsols/5, % +Count, +Templ, :Goal, -List, +Tail
bagof/3, % +Templ, :Goal, -List
setof/3 % +Templ, :Goal, -List
]).
:- meta_predicate
findall(?, 0, -),
findall(?, 0, -, ?),
findnsols(+, ?, 0, -),
findnsols(+, ?, 0, -, ?),
bagof(?, ^, -),
setof(?, ^, -).
:- noprofile((
findall/4,
findall/3,
findnsols/4,
findnsols/5,
bagof/3,
setof/3,
findall_loop/4)).
:- '$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)
).
%! findnsols(+Count, @Template, :Goal, -List) is nondet.
%! findnsols(+Count, @Template, :Goal, -List, ?Tail) is nondet.
%
% True when List is the next chunk of maximal Count instantiations
% of Template that reprensents a solution of Goal. For example:
%
% ==
% ?- findnsols(5, I, between(1, 12, I), L).
% L = [1, 2, 3, 4, 5] ;
% L = [6, 7, 8, 9, 10] ;
% L = [11, 12].
% ==
%
% @compat Ciao, but the SWI-Prolog version is non-deterministic.
% @error domain_error(not_less_than_zero, Count) if Count is less
% than 0.
% @error type_error(integer, Count) if Count is not an integer.
findnsols(Count, Template, Goal, List) :-
findnsols(Count, Template, Goal, List, []).
findnsols(Count, Template, Goal, List, Tail) :-
integer(Count),
!,
findnsols2(count(Count), Template, Goal, List, Tail).
findnsols(Count, Template, Goal, List, Tail) :-
Count = count(Integer),
integer(Integer),
!,
findnsols2(Count, Template, Goal, List, Tail).
findnsols(Count, _, _, _, _) :-
'$type_error'(integer, Count).
findnsols2(Count, Template, Goal, List, Tail) :-
nsols_count(Count, N), N > 0,
!,
copy_term(Template+Goal, Templ+G),
setup_call_cleanup(
'$new_findall_bag',
findnsols_loop(Count, Templ, G, List, Tail),
'$destroy_findall_bag').
findnsols2(Count, _, _, List, Tail) :-
nsols_count(Count, 0),
!,
Tail = List.
findnsols2(Count, _, _, _, _) :-
nsols_count(Count, N),
'$domain_error'(not_less_than_zero, N).
findnsols_loop(Count, Templ, Goal, List, Tail) :-
nsols_count(Count, FirstStop),
State = state(FirstStop),
( call_cleanup(Goal, Det=true),
'$add_findall_bag'(Templ, Found),
Det \== true,
arg(1, State, Found),
'$collect_findall_bag'(List, Tail),
( '$suspend_findall_bag'
; nsols_count(Count, Incr),
NextStop is Found+Incr,
nb_setarg(1, State, NextStop),
fail
)
; '$collect_findall_bag'(List, Tail)
).
nsols_count(count(N), N).
%! 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) :-
'$free_variable_set'(Templ^Goal0, Goal, Vars),
( Vars == v
-> findall(Templ, Goal, List),
List \== []
; findall(Vars-Templ, Goal, Answers),
bind_bagof_keys(Answers,_),
keysort(Answers, Sorted),
pick(Sorted, Vars, List)
).
%! bind_bagof_keys(+VarsTemplPairs, -SharedVars)
%
% Establish a canonical binding of the _vars_ structures. This
% code was added by Ulrich Neumerkel in commit
% 1bf9e87900b3bbd61308e80a784224c856854745.
bind_bagof_keys([], _).
bind_bagof_keys([W-_|WTs], Vars) :-
term_variables(W, Vars, _),
bind_bagof_keys(WTs, Vars).
pick(Bags, Vars1, Bag1) :-
pick_first(Bags, Vars0, Bag0, RestBags),
select_bag(RestBags, Vars0, Bag0, Vars1, Bag1).
select_bag([], Vars0, Bag0, Vars1, Bag1) :- % last one: deterministic
!,
Vars0 = Vars1,
Bag0 = Bag1.
select_bag(_, Vars, Bag, Vars, Bag).
select_bag(RestBags, _, _, Vars1, Bag1) :-
pick(RestBags, Vars1, Bag1).
%! pick_first(+Bags, +Vars, -Bag1, -RestBags) is semidet.
%
% Pick the first result-bag from the list of Templ-Answer. Note
% that we pick all elements that are equal under =@=, but because
% the variables in the witness are canonized this is the same as ==.
%
% @param Bags List of Templ-Answer
% @param Vars Initial Templ (for rebinding variables)
% @param Bag1 First bag of results
% @param RestBags Remaining Templ-Answer
pick_first([Vars-Templ|T0], Vars, [Templ|T], RestBag) :-
pick_same(T0, Vars, T, RestBag).
pick_same([V-H|T0], Vars, [H|T], Bag) :-
V == Vars,
!,
pick_same(T0, Vars, T, Bag).
pick_same(Bag, _, [], Bag).
%! setof(+Var, +Goal, -Set) is semidet.
%
% Equivalent to bagof/3, but sorts the resulting bag and removes
% duplicate answers. We sort immediately after the findall/3,
% removing duplicate Templ-Answer pairs early.
setof(Templ, Goal0, List) :-
'$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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