added example 2.3_5

2.3_5.pl

+% nacteni:
+/* ['2.3_5.pl']. */
+
+del1(A,[A|T],T).
+del1(A,[H|T1],[H|T2]) :- del1(A,T1,T2).
+
+insert(A,L,[A|L]).
+insert(A,[H|T1],[H|T2]):- insert(A,T1,T2).
+
+perm1([],[]).
+perm1([H|T],L):- perm1(T,V), insert(H,V,L).
+
+perm2([],[]).
+perm2(L,[X|P]) :- del1(X,L,L1),perm2(L1,P).
+
+perm3([],[]).
+perm3(L,[H|T]):- append(A,[H|B],L),append(A,B,L1), perm3(L1,T).
+
+% demonstracni vypis
+
+  % abychom se vyhli varovanim "Redefined static procedure ..."
+:- dynamic
+       write_all_X/3,
+       start/0.
+       
+write_all_X(Goal,X,Name):-
+            call(Goal),write('  '),write(Name),write(' = '),write(X),nl,fail.
+write_all_X(_,_,_).
+
+start:- 
+    write('Prace se seznamy - permutace'),nl,
+    write('-------------------------------'),nl,
+    write('perm1 napsany pomoci insert, vysledek volani "perm1([1,2,3],L)" :'), 
+    nl, write_all_X(perm1([1,2,3],L), L, 'L'),nl,
+
+    write('Pro blizsi porozumneni si vyzkousejte perm1, perm2 (reseny '), nl, 
+    write('pomoci del1) a perm3 (s append) s trasovanim, napr. takto:'), nl,
+    write('trace, perm1([1,2,3],L).'),nl,
+    write('Pozn.: Po vypsani prvniho vysledku si dalsi vyzadate stisnutim ";"').
+?-start.
+
+:- retractall(write_all_X/3).
+:- retractall(start/0).

2.3_5.py

+#!/usr/bin/env python
+# encoding=utf-8 (pep 0263)
+
+def del1_anyX(xs):
+    result_head = []
+    result_tail = xs
+    for x in xs:
+        result_tail = result_tail[1:]
+        yield (x, result_head + result_tail)
+        result_head.append(x)
+
+def insert(x, ys):
+    if not ys:
+        yield [x]
+    else:
+        result_head = []
+        result_tail = ys
+        for y in ys:
+            yield result_head + [x] + result_tail
+            result_tail = result_tail[1:]
+            result_head.append(y)
+        yield ys + [x]
+
+def perm1(xs):
+    if not xs:
+        yield []
+    else:
+        for ys in perm1(xs[1:]):
+            for zs in insert(xs[0], ys):
+                yield zs
+
+def perm2(xs):
+    if not xs:
+        yield []
+    else:
+        for y, ys in del1_anyX(xs):
+            for zs in perm2(ys):
+                yield [y] + zs
+
+def perm3(xs):
+    if not xs:
+        yield []
+    else:
+        result_head = []
+        result_tail = xs
+        for x in xs:
+            result_tail = result_tail[1:]
+            for ys in perm3(result_head + result_tail):
+                yield [x] + ys
+            result_head.append(x)
+
+# demonstracni vypis
+if __name__ == "__main__":
+    print("Prace se seznamy - permutace")
+    print("-------------------------------\n")
+    print("perm1 napsany pomoci insert")
+    print("Vysledek volani perm1([1, 2, 3]): %s\n" % \
+            list(perm1([1, 2, 3])))
+
+    print("perm2 napsany pomoci del1_anyX")
+    print("Vysledek volani perm2([1, 2, 3]): %s\n" % \
+            list(perm2([1, 2, 3])))
+
+    print("perm3 napsany pomoci pruchodu seznamem")
+    print("Vysledek volani perm3([1, 2, 3]): %s\n" % \
+            list(perm3([1, 2, 3])))