Helfer Swiqueens3

Jan Burse, erstellt 15. Sep 2018
/**
* CLP(FD) Prolog code for eight queens puzzle.
* With balance/3 and setup_balance/3 test cases.
* SWI-Prolog version.
*
* Originally conceived in by Max Bezzel for the 8x8 checker board.
* Used by Edsger Dijkstra to illustrate the
* Depth-first backtracking search algorithm.
*
* Warranty & Liability
* To the extent permitted by applicable law and unless explicitly
* otherwise agreed upon, XLOG Technologies GmbH makes no warranties
* regarding the provided information. XLOG Technologies GmbH assumes
* no liability that any problems might be solved with the information
* provided by XLOG Technologies GmbH.
*
* Rights & License
* All industrial property rights regarding the information - copyright
* and patent rights in particular - are the sole property of XLOG
* Technologies GmbH. If the company was not the originator of some
* excerpts, XLOG Technologies GmbH has at least obtained the right to
* reproduce, change and translate the information.
*
* Reproduction is restricted to the whole unaltered document. Reproduction
* of the information is only allowed for non-commercial uses. Selling,
* giving away or letting of the execution of the library is prohibited.
* The library can be distributed as part of your applications and libraries
* for execution provided this comment remains unchanged.
*
* Restrictions
* Only to be distributed with programs that add significant and primary
* functionality to the library. Not to be distributed with additional
* software intended to replace any components of the library.
*
* Trademarks
* Jekejeke is a registered trademark of XLOG Technologies GmbH.
*/
:- use_module('../compat/swidistributed').
:- use_module(library(clpfd)).
/*****************************************************************/
/* Normal Test Cases */
/*****************************************************************/
queens :-
cross(X, Y), modellabel([X,Y|_]).
queens2 :-
balance(cross(X, Y), modellabel([X,Y|_]), 2).
queens4 :-
balance(cross(X, Y), modellabel([X,Y|_]), 4).
queens8 :-
balance(cross(X, Y), modellabel([X,Y|_]), 8).
setup :-
model([X,Y|Z]), cross(X, Y), label([X,Y|Z]).
setup2 :-
setup_balance(model([X,Y|Z]), cross(X, Y), label([X,Y|Z]), 2).
setup4 :-
setup_balance(model([X,Y|Z]), cross(X, Y), label([X,Y|Z]), 4).
setup8 :-
setup_balance(model([X,Y|Z]), cross(X, Y), label([X,Y|Z]), 8).
/*****************************************************************/
/* The Queens Problem */
/*****************************************************************/
% modellabel(-List)
modellabel(X) :-
model(X),
label(X).
% model(-List)
model(X) :-
X = [_,_,_,_,_,_,_,_],
X ins 1..8,
noattack_list(X),
all_different(X).
% cross(-Integer, -Integer)
cross(X, Y) :-
between(1, 8, X),
between(1, 8, Y).
% noattack_from(+List, +Variable, +Integer)
noattack_from([], _, _).
noattack_from([Y|Z], X, N) :-
X+N #\= Y,
Y+N #\= X,
M is N+1,
noattack_from(Z, X, M).
% noattack_list(+List)
noattack_list([]).
noattack_list([X|Y]) :-
noattack_from(Y, X, 1),
noattack_list(Y).

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