added example 3.1_3

3.1_3.pl

+% 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).

3.1_3.py

+#!/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())))

3.1_3.py.out

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