added example 2.4.1_6

% nacteni:

/* ['2.4.1_6.pl']. */

append([],L,L).

append([H|T1],L2,[H|T]) :- append(T1,L2,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(_,_,_).

write_all_XY(Goal,X,XName,Y,YName):-

            call(Goal),write('  '),write(XName),write(' = '),write(X),

                       write('  '),write(YName),write(' = '),write(Y),

                       nl, fail.

write_all_XY(_,_,_,_,_).

start:- 

    write('Prace se seznamy - append'),nl,

    write('-------------------------------'),nl, nl,

    write('vicesmernost predikatu append:'),nl,    

    write('Vysledek volani "append([a,b],[c,d],L)":'),nl,

    write_all_X(append([a,b],[c,d],L), L, 'L'),nl,

    write('Vysledek volani "append(X,[c,d],[a,b,c,d ]).":'),nl,

    write_all_X(append(X,[c,d],[a,b,c,d ]), X, 'X'),nl,

    write('Vysledek volani "append(X,Y,[a,b,c])":'),nl,

    write_all_XY(append(X,Y,[a,b,c]), X, 'X', Y, 'Y'),nl.

?-start.

:- retractall(write_all_X/3).

:- retractall(start/0).

#!/usr/bin/env python

# encoding=utf-8 (pep 0263)

def append(xs, ys):

    if not xs:

        return ys

    else:

        return [xs[0]] + append(xs[1:], ys)

def append_anyXs(ys, zs):

    if ys == zs:

        return []

    else:

        if zs:

            return [zs[0]] + append_anyXs(ys, zs[1:])

        else:

            raise ValueError("ys neni sufixem zs")

def append_anyXsYs(zs):

    yield ([], zs)

    if zs:

        for xs, ys in append_anyXsYs(zs[1:]):

            yield ([zs[0]] + xs, ys)

# demonstracni vypis

if __name__ == "__main__":

    print("Prace se seznamy - append")

    print("-------------------------------\n")

    print("vicesmerne implementace funkce append:\n")

    print("Vysledek volani append(['a', 'b'], ['c', 'd']): %s\n" % \

            append(['a', 'b'], ['c', 'd']))

    print("Vysledek volani append_anyXs(['c', 'd'], ['a', 'b', 'c', 'd']): %s\n" % \

            append_anyXs(['c', 'd'], ['a', 'b', 'c', 'd']))

    print("Vysledek volani append_anyXsYs(['a', 'b', 'c']): %s\n" % \

            list(append_anyXsYs(['a', 'b', 'c'])))