2 files changed, 25 insertions, 6 deletions
diff --git a/prolog/problems/family_relations/sister_2/common.py b/prolog/problems/family_relations/sister_2/common.py
index 627648c..c112a9c 100644
--- a/prolog/problems/family_relations/sister_2/common.py
+++ b/prolog/problems/family_relations/sister_2/common.py
@@ -23,8 +23,9 @@ sister(X, Y) :-
 hint_type = {
     'x_must_be_female': Hint('x_must_be_female'),
     'common_parent_needed': Hint('common_parent_needed'),
-    'y_can_be_of_any_gender': Hint('Y_can_be_of_any_gender'),
+    'y_can_be_of_any_gender': Hint('y_can_be_of_any_gender'),
     'x_y_must_be_different': Hint('x_y_must_be_different'),
+    'neq_used_too_early': Hint('neq_used_too_early'),
 }
 
 test_cases = [
@@ -121,10 +122,17 @@ def hint(program, solved_problems):
 
         # X and Y must be different
         # this is the last code-specific hint (when everything else doesn't trigger anymore)
-        if prolog.engine.ask_truth(engine_id,
+        if prolog.util.Token('NEQ', '\==') not in tokens and prolog.engine.ask_truth(engine_id,
             'setof(X, (member(X, [sally, nevia, vanessa]), sister(X, X)), L), length(L, 3)'):
             return [{'id': 'x_y_must_be_different'}]
 
+        # X and Y must be different, but the user used '\=='
+        # most likely this means that \== was used before X and Y are known
+        # this is the last code-specific hint (when everything else doesn't trigger anymore)
+        if prolog.util.Token('NEQ', '\==') in tokens and prolog.engine.ask_truth(engine_id,
+            'setof(X/Y, sister(X, Y), L), member(nevia/nevia, L), member(sally/sally, L), member(vanessa/vanessa, L)'):
+            return [{'id': 'neq_used_too_early'}]
+
         # last hints are connected with programming style
         # here, this means detecting such code:
         # parent(P1, X), parent(P2, Y), P1 == P2 (or P1 = P2)
diff --git a/prolog/problems/family_relations/sister_2/sl.py b/prolog/problems/family_relations/sister_2/sl.py
index d69b56c..cb51592 100644
--- a/prolog/problems/family_relations/sister_2/sl.py
+++ b/prolog/problems/family_relations/sister_2/sl.py
@@ -21,14 +21,16 @@ potem je <code>X</code> sestra od <code>Y</code>.</p>''',
 ]
 
 hint = {
-    'x_y_must_be_different': '''\
+    'x_y_must_be_different': [{'message': '''\
 <p><img src="[%@resource Prolog_sister_04.svg%]" /></p>
 <p>Si pomislil, da sta <code>X</code> in <code>Y</code> lahko ista oseba? Poskusi naslednjo poizvedbo:</p>
 <pre>
 ?- sister(sally, Y).
-</pre>
-<p>VEČ... Kako naredim, da sta X in Y različna?</p>
-''',
+</pre>''', 'linkText': 'Kako lahko preverim, da sta <code>X</code> in <code>Y</code> različna?'},
+'''\
+<p>S pomočjo operatorja <code>\==</code> lahko preverim, da sta <code>X</code> in <code>Y</code> med seboj različna.
+Na primer: <code>X \== Y</code></p>
+'''],
 
     'x_must_be_female': '''\
 <p><img src="[%@resource Prolog_sister_03.svg%]" /></p>
@@ -43,4 +45,13 @@ hint = {
 <p><img src="[%@resource Prolog_sister_05.svg%]" /></p>
 <p>Dobro bi bilo, da imata <code>X</code> in <code>Y</code> vsaj enega skupnega starša.</p>
 ''',
+
+    'neq_used_too_early': '''\
+<p>Si morda uporabil operator <code>\==</code> prezgodaj?</p>
+<p>Poskusi ga pomakniti bolj proti koncu. Razlog za probleme je verjetno,
+da spremenljivki, ki ju primerjaš, še nimata določene vrednosti in sta zato različni.
+Prolog ne preverja, če kasneje morda postaneta enaki, ampak samo kakšni sta v trenutku,
+ko naleti na primerjavo.</p>
+''',
+
 }