added example 3.1_3

% nacteni:

/* ['3.1_3.pl']. */

:- retractall(solution/1).

:- retractall(sol/1).

:- retractall(noattack/2).

:- retractall(template/1).

:- dynamic

       solution/1,

       sol/1,

       noattack/2,

       template/1.

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

sol([]).

sol([X/Y|Others]) :- sol(Others),

                      member(X,[1,2,3,4,5,6,7,8]),

                      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([_X1/_Y1, _X2/_Y2, _X3/_Y3, _X4/_Y4, _X5/_Y5, _X6/_Y6, _X7/_Y7, _X8/_Y8]).

% demonstracni vypis

  % abychom se vyhli varovanim "Redefined static procedure ..."

:- dynamic

       start/0.

start:- 

    write('PROBLEM OSMI DAM I'),nl,

    write('Zadejte dotaz "solution(Solution)", po vypoctu prvniho reseni'),nl,

    write('si dalsi vyzadate stisknutim ";".'),nl.

?-start.

:- retractall(start/0).

#!/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):

            for x in range(8):

                for y in range(8):

                    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)

def tisknireseni(reseni):

    return ["%d/%d" % (x+1, y+1) for (x, y) in reseni]

# demonstracni vypis

if __name__ == "__main__":

    print("PROBLEM OSMI DAM I")

    print("Volani tisknireseni(next(solution())) : %s" % \

            tisknireseni(next(solution())))

PROBLEM OSMI DAM I

Volani tisknireseni(next(solution())) : ['8/4', '7/2', '6/7', '5/3', '4/6', '3/8', '2/5', '1/1']