chore: Tweak demo

examples/demo.pl

@@ -52,11 +52,11 @@ choice(_) :- write('DEMO: Invalid choice, please try again: '), read(Choice), ch
 
 run_login_example :-
     say('Loading login example...'),
-    consult('examples/basics/repeat.pl'),
+    consult_once('examples/basics/repeat', true, true),
-    consult('examples/basics/password.pl'),
+    consult_once('examples/basics/password', true, true),
     say('Showing login/0'),
     say('You might try logging in with tibo/noaccess and john/john1.'),
-    login, login_example_loop, !,
+    login, !, login_example_loop,
     say('Login example finished.').
 
 login_example_loop :-
@@ -64,10 +64,10 @@ login_example_loop :-
 
 run_summer_example :-
     say('Loading summer example...'),
-    consult('examples/basics/summer.pl'),
+    consult_once('examples/basics/summer', clear, summer_main),
     say('Showing my_sum/1'),
     say('You might try summing 1 to 9.'),
-    my_sum, summer_example_loop, !,
+    my_sum, !, summer_example_loop,
     say('Summer example finished.').
 
 summer_example_loop :-
@@ -75,7 +75,7 @@ summer_example_loop :-
 
 run_mib_voorbeelden_example :-
     say('Loading mib_voorbeelden example...'),
-    consult('examples/meta/mib_voorbeelden.pl'), clear,
+    consult_once('examples/meta/mib_voorbeelden', clear, true),
     say('Showing example1/0'), example1, next((
     say('Showing example2/0'), example2, next((
     say('Showing example3/0'), example3)))),
@@ -83,21 +83,21 @@ run_mib_voorbeelden_example :-
 
 run_ceremony_example :-
     say('Loading ceremony example...'),
-    consult('examples/meta/ceremony.pl'), clear,
+    consult_once('examples/meta/ceremony.pl', clear, true),
     say('Showing ceremony_main/0'),
     ceremony_main,
     say('Ceremony example finished.').
 
 run_continuations_example :-
     say('Loading continuations example...'),
-    consult('examples/meta/continuations.pl'), clear,
+    consult_once('examples/meta/continuations.pl', clear, true),
     say('Showing continuations_main/0'),
     continuations_main,
     say('Continuations example finished.').
 
 run_my_list_example :-
     say('Loading my_list example...'),
-    consult('examples/meta/my_list.pl'),
+    consult_once('examples/meta/my_list.pl', true, true),
     say('Showing my_member/2'),
     showcase(my_member(X, a(b(c))), 'X', X),
     continue,
@@ -107,8 +107,8 @@ run_my_list_example :-
 
 run_interpreter :-
     say('Loading interpreter...'),
-    consult('examples/meta/ground.pl'),
+    consult_once('examples/meta/ground.pl', true, true),
-    consult('examples/meta/interpreter.pl'),
+    consult_once('examples/meta/interpreter.pl', true, true),
     say('Showing interpreter/0'),
     say('Have fun!'),
     interpreter,
@@ -119,9 +119,9 @@ run_interpreter :-
 % % % % % % % % % % %
 
 yes_or_no(Question, IfYes, IfNo) :-
-    write(Question), write(' (y/n): '),
+    write(Question), write(' (y/n) '),
     read(Answer),
-    ( ( was_yes(Answer), !, call(IfYes)) ; ( was_no(Answer), !, call(IfNo))).
+    ( ( was_yes(Answer), !, (call(IfYes) ; true)) ; ( was_no(Answer), !, (call(IfNo) ; true))).
 
 was_yes(y).
 was_yes('Y').
@@ -162,3 +162,10 @@ clear(N) :-
     nl,
     M is N - 1,
     clear(M).
+
+consult_once(File,     _, Subsequent) :-
+    consulted(File), !.
+consult_once(File, First,          _) :-
+    consult(File),
+    call(First),
+    assert(consulted(File)).