[tutor] Update assignment

examples/basics/liberty.pl

@@ -0,0 +1,31 @@
+:- dynamic declaration/1.
+
+add_declaration_first(NewDecl) :-
+    asserta(declaration(NewDecl)).
+
+add_declaration_last(NewDecl) :-
+    assertz(declaration(NewDecl)).
+
+database :-
+    add_declaration_first('Man is born free, and everywhere he is in chains.'),
+    retract(declaration(_)),
+    add_declaration_last('The revolution devours its own children.'),
+    add_declaration_first('I disapprove of what you say, but I will defend to the death your right to say it.'),
+    add_declaration_first('Give me Liberty, or give me Death!'),
+    add_declaration_last('So this is how liberty dies, with thunderous applause.').
+
+show_declarations :-
+    declaration(Decl),
+    write(Decl), nl,
+    fail.
+
+show_declarations.
+
+:- initialization(main).
+
+main :-
+    database,
+    show_declarations,
+    retractall(declaration(_)),
+    show_declarations.
+