Test Queens3

Jan Burse, erstellt 30. Jun 2019
* CLP(FD) Prolog code for eight queens puzzle.
* Originally conceived in by Max Bezzel for the 8x8 checker board.
* Used by Edsger Dijkstra to illustrate the
* Depth-first backtracking search algorithm.
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:- current_prolog_flag(dialect, jekejeke) -> true
; use_module(library(clpfd)).
:- current_prolog_flag(dialect, jekejeke)
-> use_module(library(finite/clpfd)); true.
% 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_from(Y, X, 1),
% queens3(-List)
X = [_,_,_,_,_,_,_,_],
X ins 1..8,