#!/usr/bin/env python
# encoding=utf-8 (pep 0263)

from linked_lists import Cons, Nil

def solution(n=8):
    if n == 0:
        yield Nil
    else:
        for others in solution(n-1):
            x = 9 - n
            for y in range(1, 9):
                if noattack(x, y, others):
                    yield Cons((x, y), others)

def noattack(x, y, others):
    if others == Nil:
        return True
    else:
        x1, y1 = others.head
        return x != x1 and y != y1 and y1-y != x1-x and y1-y != x-x1 and \
               noattack(x, y, others.tail)

# demonstracni vypis
if __name__ == "__main__":
    print("PROBLEM OSMI DAM I")
    print("Volani next(solution()) : %s" % next(solution()))

PROBLEM OSMI DAM I
Volani next(solution()) : [(1, 4), (2, 2), (3, 7), (4, 3), (5, 6), (6, 8), (7, 5), (8, 1)]

% nacteni:
/* ['3.2_4.pl']. */

solution(S) :- template(S), sol(S).

sol([]).
sol([X/Y|Others]) :- sol(Others), member(Y,[1,2,3,4,5,6,7,8]),
                      noattack(X/Y,Others).

noattack(_,[]).
noattack(X/Y,[X1/Y1|Others]) :- X=\=X1, Y=\=Y1, Y1-Y=\=X1-X, Y1-Y=\=X-X1,
                                noattack(X/Y,Others).

template([1/_Y1,2/_Y2,3/_Y3,4/_Y4,5/_Y5,6/_Y6,7/_Y7,8/_Y8]).

% demonstracni vypis

start:- 
    write('PROBLEM OSMI DAM II - jeden sloupec pro kazdou damu'),nl,
    write('Prvni reseni solution(Solution) - vsimnete si zrychleni oproti verzi I:'),nl,
    solution(Solution),write(Solution),nl.
?-start.

PROBLEM OSMI DAM II - jeden sloupec pro kazdou damu
Prvni reseni solution(Solution) - vsimnete si zrychleni oproti verzi I:
[1/4,2/2,3/7,4/3,5/6,6/8,7/5,8/1]