New problems with hints for famrel section added.

This practically completes famrel section without some details.

16 files changed, 835 insertions, 21 deletions

diff --git a/prolog/problems/family_relations/ancestor_2/common.py b/prolog/problems/family_relations/ancestor_2/common.py
index 473fa27..873b87b 100644
--- a/prolog/problems/family_relations/ancestor_2/common.py
+++ b/prolog/problems/family_relations/ancestor_2/common.py
@@ -13,3 +13,104 @@ ancestor(X, Y) :-
   parent(X, Z),
   ancestor(Z, Y).
 '''
+
+hint_type = {
+    'gender_is_irrelevant': Hint('gender_is_irrelevant'),
+    'grandparent_used': Hint('grandparent_used'),
+    'base_case': Hint('base_case'),
+    'ancestor_to_oneself': Hint('ancestor_to_oneself'),
+    'descendant_need_not_be_parent': Hint('descendant_need_not_be_parent'),
+    'wrong_direction': Hint('wrong_direction'),
+}
+
+test_cases = [
+    # TODO
+]
+
+def test(program, solved_problems):
+    code = (program + '\n' +
+            server.problems.solutions_for_problems('prolog', solved_problems) + '\n' +
+            server.problems.load_facts('prolog', facts).facts)
+
+    engine_id = None
+    try:
+        engine_id, output = prolog.engine.create(code=code, timeout=1.0)
+        if not engine_id or 'error' in map(itemgetter(0), output):
+            # Engine creation failed, or syntax error in code.
+            return 0, len(test_cases)
+
+        n_correct = 0
+        for query, answers in test_cases:
+            # Limit inferences for each solution to curb unbounded recursion.
+            limited = 'call_with_inference_limit(({}), 100000, _)'.format(query)
+            if prolog.engine.check_answers(engine_id, query=limited, answers=answers, timeout=1.0):
+                n_correct += 1
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
+    passed = n_correct == len(test_cases)
+    hints = [{'id': 'test_results', 'args': {'passed': n_correct, 'total': len(test_cases)}}]
+    return passed, hints
+
+def hint(program, solved_problems):
+    tokens = prolog.util.tokenize(program)
+
+    code = (program + '\n' +
+            server.problems.solutions_for_problems('prolog', solved_problems) + '\n' +
+            server.problems.load_facts('prolog', facts).facts)
+
+    engine_id = None
+    try:
+        engine_id, output = prolog.engine.create(code=code, timeout=1.0)
+        if not engine_id:
+            raise Exception('Prolog engine failed to create.')
+
+        # gender testing is redundant
+        # this is not necessarily wrong, but worth mentioning anyway
+        targets = [prolog.util.Token('NAME', 'male'), prolog.util.Token('NAME', 'female')]
+        pos = [(t.pos, t.pos + len(t.val)) for t in tokens if t in targets]
+        if pos:
+            # TODO: resolve how highlighting info is communicated
+            return [{'id': 'gender_is_irrelevant', 'highlight': pos}]
+
+        # grandparent is a sign of complications
+        # it's likely used instead of recursion
+        targets = [prolog.util.Token('NAME', 'grandparent')]
+        pos = [(t.pos, t.pos + len(t.val)) for t in tokens if t in targets]
+        if pos:
+            # TODO: resolve how highlighting info is communicated
+            return [{'id': 'grandparent_used', 'highlight': pos}]
+
+        # missing/failed base case
+        # TODO: how will ask_truth handle/return timeouts...
+        # TODO: timeout is the same as fail in this particular case
+        if prolog.engine.ask_truth(engine_id,
+            'parent(X, Y), \+ ancestor(X, Y)'):
+            return [{'id', 'base_case'}]
+
+        # ancestor to oneself
+        if prolog.engine.ask_truth(engine_id, 'ancestor(X, X)'):
+            return [{'id', 'ancestor_to_oneself'}]
+
+        # Y does not necessarily need to be a parent
+        if prolog.engine.ask_one(engine_id,
+            'ancestor(_, Y), \+ parent(Y, _)') == 'false':
+            return [{'id': 'descendant_need_not_be_parent'}]
+
+        # descendant instead of ancestor (wrong direction)
+        # warning: knowledge base dependent
+        if prolog.engine.ask_truth(engine_id,
+            'findall(_, ancestor(william, X), L1), length(L1, 2), \
+             findall(_, ancestor(X, william), L2), length(L2, 6)'):
+            return [{'id', 'wrong_direction'}]
+
+    except socket.timeout as ex:
+        pass
+
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
+    return None
+
diff --git a/prolog/problems/family_relations/ancestor_2/sl.py b/prolog/problems/family_relations/ancestor_2/sl.py
new file mode 100644
index 0000000..76c2bea
--- /dev/null
+++ b/prolog/problems/family_relations/ancestor_2/sl.py
@@ -0,0 +1,62 @@
+# coding=utf-8
+
+id = 100
+name = 'ancestor/2'
+slug = 'X je prednik od Y'
+
+description = '''\
+<p><code>ancestor(X, Y)</code>: <code>X</code> je prednik (oče, mama, dedek, ...) od <code>Y</code>.</p>
+<pre>
+  ?- ancestor(patricia, X).
+    X = john ;
+    X = michael ;
+    X = michelle.
+</pre>'''
+
+plan = ['''\
+<p>Sedaj pa bo potrebna rekurzija... kako lahko problem prevedem na (en korak) manjši problem?</p>
+<p><img src="Ancestor-3.png" /></p>
+<p>Loni naj zbriše imena relacij (parent, ancestor) s te slike!</p>
+''', '''\
+<p><img src="Ancestor-3.png" /></p>
+''', '''\
+<p>Če je <code>X</code> starš od nekega <code>Z</code> in je
+ta <code>Z</code> prednik od <code>Y</code>,
+potem je <code>X</code> tudi prednik od <code>Y</code>.</p>
+''']
+
+hint = {
+    'gender_is_irrelevant': '''\
+<p>Je spol res pomemben?</p>
+''',
+
+    'grandparent_used': '''\
+<p>Rešitev z "grandparent" bo premalo splošna, poskusi nadomestiti to z rekurzijo.
+Skratka, poskusi prevesti na "manjši" problem, npr. prednik v enem koraku manj
+(en korak bližji prednik)...</p>
+''',
+
+    'base_case': '''\
+<p>Si pomislil na robni pogoj? Kaj je najbolj enostaven par (prednik, potomec)?</p>
+<p><img src="Ancestor-1.png" /></p>
+''',
+
+    'ancestor_to_oneself': '''\
+<p>Kako je lahko nekdo prednik samemu sebi?</p>
+''',
+
+    'descendant_need_not_be_parent': '''\
+<p>Potomec <code>Y</code> pravzaprav ne rabi imeti otrok...</p>
+''',
+
+    'wrong_direction': '''\
+<p>Si morda sprogramiral ravno obratno in zamenjal prednika s potomcem?
+<code>X</code> naj bo prednik od <code>Y</code> in ne obratno!</p>
+''',
+
+#     'interesting_tidbit': '''\
+# <p>Zanimivost: nalogo bi lahko rešil tudi z uporabo rešitve za relacijo "sister".
+# Teta je namreč sestra od starša od <code>Y</code>.</p>
+# ''',
+}
+
diff --git a/prolog/problems/family_relations/aunt_2/common.py b/prolog/problems/family_relations/aunt_2/common.py
index f0af2dc..ed291fc 100644
--- a/prolog/problems/family_relations/aunt_2/common.py
+++ b/prolog/problems/family_relations/aunt_2/common.py
@@ -17,3 +17,103 @@ aunt(X, Y) :-
   sister98(X, Z),
   parent(Z, Y).
 '''
+
+hint_type = {
+    'x_and_y_mixed_up': Hint('x_and_y_mixed_up'),
+    'precedence_fail': Hint('precedence_fail'),
+    'x_must_be_female': Hint('x_must_be_female'),
+    'aunt_vs_mother': Hint('aunt_vs_mother'),
+    'x_need_not_be_parent': Hint('x_need_not_be_parent'),
+    'y_need_not_be_parent': Hint('y_need_not_be_parent'),
+}
+
+test_cases = [
+    # TODO
+]
+
+def test(program, solved_problems):
+    code = (program + '\n' +
+            server.problems.solutions_for_problems('prolog', solved_problems) + '\n' +
+            server.problems.load_facts('prolog', facts).facts)
+
+    engine_id = None
+    try:
+        engine_id, output = prolog.engine.create(code=code, timeout=1.0)
+        if not engine_id or 'error' in map(itemgetter(0), output):
+            # Engine creation failed, or syntax error in code.
+            return 0, len(test_cases)
+
+        n_correct = 0
+        for query, answers in test_cases:
+            # Limit inferences for each solution to curb unbounded recursion.
+            limited = 'call_with_inference_limit(({}), 100000, _)'.format(query)
+            if prolog.engine.check_answers(engine_id, query=limited, answers=answers, timeout=1.0):
+                n_correct += 1
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
+    passed = n_correct == len(test_cases)
+    hints = [{'id': 'test_results', 'args': {'passed': n_correct, 'total': len(test_cases)}}]
+    return passed, hints
+
+def hint(program, solved_problems):
+    tokens = prolog.util.tokenize(program)
+
+    code = (program + '\n' +
+            server.problems.solutions_for_problems('prolog', solved_problems) + '\n' +
+            server.problems.load_facts('prolog', facts).facts)
+
+    engine_id = None
+    try:
+        engine_id, output = prolog.engine.create(code=code, timeout=1.0)
+        if not engine_id:
+            raise Exception('Prolog engine failed to create.')
+
+        # X and Y mixed up
+        # warning: knowledge base dependent
+        # independent: match on findall(X/Y, (sister(Y, P), parent(P, X)), L)
+        if prolog.engine.ask_truth(engine_id,
+            'findall(X/Y, aunt(X, Y), \
+             [vanessa/sally, patricia/sally, joanne/melanie, john/vanessa, susan/patricia])'):
+            return [{'id', 'x_and_y_mixed_up'}]
+
+        # precedence fail (AND block vs OR block)
+        # case in point: female(X), parent(P, Y), brother(P, X) ; sister(P, X)
+        # warning: knowledge base dependent
+        if prolog.util.Token('SEMI', ';') in tokens and prolog.engine.ask_truth(engine_id,
+            'findall(_, aunt(X, Y), L), length(L, 15)'):
+            return [{'id', 'precedence_fail'}]
+
+        # X must be female
+        if prolog.engine.ask_truth(engine_id,
+            'aunt(X, _), male(X)'):
+            return [{'id', 'x_must_be_female'}]
+
+        # X and P can be the same person
+        # this can occur if the problem is not solved using sister/2
+        if prolog.engine.ask_truth(engine_id,
+            'aunt(X, Y), mother(X, Y)'):
+            return [{'id', 'aunt_vs_mother'}]
+
+        # X does not necessarily need to be a parent
+        # perhaps risky as only one aunt that is not a parent exists in DB (melanie)
+        if prolog.engine.ask_one(engine_id,
+            'aunt(X, _), \+ parent(X, _)') == 'false':
+            return [{'id': 'x_need_not_be_parent'}]
+
+        # Y does not necessarily need to be a parent
+        # perhaps risky as only one such nephew exists in DB (susan)
+        if prolog.engine.ask_one(engine_id,
+            'aunt(_, Y), \+ parent(Y, _)') == 'false':
+            return [{'id': 'y_need_not_be_parent'}]
+
+    except socket.timeout as ex:
+        pass
+
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
+    return None
+
diff --git a/prolog/problems/family_relations/aunt_2/sl.py b/prolog/problems/family_relations/aunt_2/sl.py
new file mode 100644
index 0000000..95fc6b2
--- /dev/null
+++ b/prolog/problems/family_relations/aunt_2/sl.py
@@ -0,0 +1,60 @@
+# coding=utf-8
+
+id = 98
+name = 'aunt/2'
+slug = 'X je teta od Y'
+
+description = '''\
+<p><code>aunt(X, Y)</code>: <code>X</code> je teta od <code>Y</code>.</p>
+<pre>
+  ?- aunt(sally, X).
+    X = vanessa ;
+    X = patricia.
+</pre>'''
+
+plan = ['''\
+<p>Morda lahko uporabiš rešitev kakšne prejšnje naloge?</p>
+<p><img src="Aunt-5.png" /></p>
+<p>Loni naj zbriše imena relacij (parent, sister) s te slike!</p>
+''', '''\
+<p><img src="Aunt-5.png" /></p>
+''', '''\
+<p>Če je <code>X</code> sestra od starša od <code>Y</code>,
+potem je <code>X</code> teta od <code>Y</code>.</p>
+''']
+
+hint = {
+    'x_and_y_mixed_up': '''\
+<p><code>X</code> mora biti teta od <code>Y</code>, ne obratno.</p>
+''',
+
+    'precedence_fail': '''\
+<p>Si morda narobe upošteval prioriteto operatorjev IN ter ALI?</p>
+<p>Operator IN veže močneje od ALI, če želiš spremeniti prioriteto,
+lahko uporabiš oklepaje.</p>
+''',
+
+    'x_must_be_female': '''\
+<p>Teta je navadno ženskega spola.</p>
+''',  # TODO: Loni should mark female gender on some aunt hints!
+
+    'aunt_vs_mother': '''\
+<p>Kako je teta lahko hkrati še mama od <code>Y</code>?
+Si morda pozabil, da teta in starš od <code>Y</code> ne smeta biti ista oseba?</p>
+<p><img src="Aunt-4.png" /></p>
+''',
+
+    'x_need_not_be_parent': '''\
+<p><code>X</code> pravzaprav ne rabi imeti otrok, da je lahko teta od nekoga...</p>
+''',
+
+    'y_need_not_be_parent': '''\
+<p>Nečak ali nečakinja <code>Y</code> pravzaprav ne rabi imeti otrok, da ima teto...</p>
+''',
+
+    'interesting_tidbit': '''\
+<p>Zanimivost: nalogo bi lahko rešil tudi z uporabo rešitve za relacijo "sister".
+Teta je namreč sestra od starša od <code>Y</code>.</p>
+''',    # TODO: only trigger if sister is not part of correct solution
+}
+
diff --git a/prolog/problems/family_relations/brother_2/common.py b/prolog/problems/family_relations/brother_2/common.py
index 0df2d73..327e746 100644
--- a/prolog/problems/family_relations/brother_2/common.py
+++ b/prolog/problems/family_relations/brother_2/common.py
@@ -24,7 +24,7 @@ brother(X, Y) :-
 hint_type = {
     'x_must_be_male': Hint('x_must_be_male'),
     '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'),
 }
 
@@ -87,14 +87,12 @@ def hint(program, solved_problems):
         # Y can be of any gender, incl. female
         if prolog.engine.ask_one(engine_id,
             'brother(_, Y), female(Y)') == 'false':
-            return [{'id': 'Y_can_be_of_any_gender'}]
+            return [{'id': 'y_can_be_of_any_gender'}]
 
         # X and Y must be different
-        ans = prolog.engine.ask_one(engine_id,
-            'setof(X, (member(X, [william, alessandro, andrew]), brother(X, X)), L), length(L, N).')
-        # TODO this barfs if ans is 'false'
-        #if ans.get('N') == '3':
-        #    return [{'id': 'x_y_must_be_different'}]
+        if prolog.engine.ask_truth(engine_id,
+            'setof(X, (member(X, [william, alessandro, andrew]), brother(X, X)), L), length(L, 3)'):
+            return [{'id': 'x_y_must_be_different'}]
 
     except socket.timeout as ex:
         pass
diff --git a/prolog/problems/family_relations/brother_2/sl.py b/prolog/problems/family_relations/brother_2/sl.py
index 116a968..2176bd8 100644
--- a/prolog/problems/family_relations/brother_2/sl.py
+++ b/prolog/problems/family_relations/brother_2/sl.py
@@ -38,7 +38,7 @@ hint = {
 <p>Brat je navadno moškega spola.</p>
 ''',
 
-    'Y_can_be_of_any_gender': '''\
+    'y_can_be_of_any_gender': '''\
 <p><code>Y</code> je pravzaprav lahko poljubnega spola.</p>
 ''',
 
diff --git a/prolog/problems/family_relations/cousin_2/common.py b/prolog/problems/family_relations/cousin_2/common.py
index 7cd6392..d95babd 100644
--- a/prolog/problems/family_relations/cousin_2/common.py
+++ b/prolog/problems/family_relations/cousin_2/common.py
@@ -26,3 +26,98 @@ cousin(X, Y) :-
     ;
     sister99(PX, PY) ).
 '''
+
+hint_type = {
+    'gender_is_irrelevant': Hint('gender_is_irrelevant'),
+    'precedence_fail': Hint('precedence_fail'),
+    'cousin_vs_sibling': Hint('cousin_vs_sibling'),
+    'cousin_to_oneself': Hint('cousin_to_oneself'),
+    'cousin_need_not_be_parent': Hint('cousin_need_not_be_parent'),
+}
+
+test_cases = [
+    # TODO
+]
+
+def test(program, solved_problems):
+    code = (program + '\n' +
+            server.problems.solutions_for_problems('prolog', solved_problems) + '\n' +
+            server.problems.load_facts('prolog', facts).facts)
+
+    engine_id = None
+    try:
+        engine_id, output = prolog.engine.create(code=code, timeout=1.0)
+        if not engine_id or 'error' in map(itemgetter(0), output):
+            # Engine creation failed, or syntax error in code.
+            return 0, len(test_cases)
+
+        n_correct = 0
+        for query, answers in test_cases:
+            # Limit inferences for each solution to curb unbounded recursion.
+            limited = 'call_with_inference_limit(({}), 100000, _)'.format(query)
+            if prolog.engine.check_answers(engine_id, query=limited, answers=answers, timeout=1.0):
+                n_correct += 1
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
+    passed = n_correct == len(test_cases)
+    hints = [{'id': 'test_results', 'args': {'passed': n_correct, 'total': len(test_cases)}}]
+    return passed, hints
+
+def hint(program, solved_problems):
+    tokens = prolog.util.tokenize(program)
+
+    code = (program + '\n' +
+            server.problems.solutions_for_problems('prolog', solved_problems) + '\n' +
+            server.problems.load_facts('prolog', facts).facts)
+
+    engine_id = None
+    try:
+        engine_id, output = prolog.engine.create(code=code, timeout=1.0)
+        if not engine_id:
+            raise Exception('Prolog engine failed to create.')
+
+        # gender testing is redundant
+        # this is not necessarily wrong, but worth mentioning anyway
+        targets = [prolog.util.Token('NAME', 'male'), prolog.util.Token('NAME', 'female')]
+        pos = [(t.pos, t.pos + len(t.val)) for t in tokens if t in targets]
+        if pos:
+            # TODO: resolve how highlighting info is communicated
+            return [{'id': 'gender_is_irrelevant', 'highlight': pos}]
+
+        # precedence fail (AND block vs OR block)
+        # case in point: parent(PX, X), parent(PY, Y), brother(PX, PY) ; sister(PX, PY)
+        #  or this case: parent(PX, X), parent(PY, Y), sister(PX, PY) ; brother(PX, PY)
+        # warning: knowledge base dependent
+        if prolog.util.Token('SEMI', ';') in tokens and prolog.engine.ask_truth(engine_id,
+            'findall(_, cousin(X, Y), L), (length(L, 14) ; length(L, 16))'):
+            return [{'id', 'precedence_fail'}]
+
+        # cousin should not be brother or sister
+        # common parent, probably solved via grandparent
+        if prolog.engine.ask_truth(engine_id,
+            'cousin(X, Y), (brother(X, Y) ; sister(X, Y))'):
+            return [{'id', 'cousin_vs_sibling'}]
+
+        # cousin to him/herself
+        # just common grandparent is not enough
+        if prolog.engine.ask_truth(engine_id, 'cousin(X, X)'):
+            return [{'id', 'cousin_to_oneself'}]
+
+
+        # X (or Y) does not necessarily need to be a parent
+        # cousin is a symmetrical relation, so X and Y are covered by this
+        if prolog.engine.ask_one(engine_id,
+            'cousin(X, _), \+ parent(X, _)') == 'false':
+            return [{'id': 'cousin_need_not_be_parent'}]
+
+    except socket.timeout as ex:
+        pass
+
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
+    return None
+
diff --git a/prolog/problems/family_relations/cousin_2/sl.py b/prolog/problems/family_relations/cousin_2/sl.py
new file mode 100644
index 0000000..ebecf8d
--- /dev/null
+++ b/prolog/problems/family_relations/cousin_2/sl.py
@@ -0,0 +1,63 @@
+# coding=utf-8
+
+id = 99
+name = 'cousin/2'
+slug = 'X je bratranec ali sestrična od Y'
+
+description = '''\
+<p><code>cousin(X, Y)</code>: <code>X</code> je bratranec ali sestrična od <code>Y</code>.</p>
+<pre>
+  ?- cousin(andrew, X).
+    X = vanessa ;
+    X = patricia.
+</pre>'''
+
+plan = ['''\
+<p>Verjetno bi se sedaj splačalo uporabiti rešitev kakšne prejšnje naloge?</p>
+<p><img src="Cousin-1.png" /></p>
+<p>Loni naj zbriše imena relacij (parent, sister) s te slike!</p>
+<p>Seveda se da rešiti tudi brez prejšnjih rešitev... MORE</p>
+<p><img src="Cousin-3.png" /></p>
+<p>Loni naj zbriše imena relacij (parent, sister) s te slike!</p>
+''', '''\
+<p><img src="Cousin-1.png" /></p>
+''', '''\
+<p>Če je <code>PX</code> starš od <code>X</code> in je
+<code>PY</code> starš od <code>Y</code> ter sta
+<code>PX</code> in <code>PY</code> brat ali sestra,
+potem je <code>X</code> bratranec/sestrična od <code>Y</code>.</p>
+''']
+
+hint = {
+    'gender_is_irrelevant': '''\
+<p>Je spol res pomemben?</p>
+''',
+
+    'precedence_fail': '''\
+<p>Si morda narobe upošteval prioriteto operatorjev IN ter ALI?</p>
+<p>Operator IN veže močneje od ALI, če želiš spremeniti prioriteto,
+lahko uporabiš oklepaje.</p>
+''',
+
+    'cousin_vs_sibling': '''\
+<p>Kako je lahko bratranec/sestrična hkrati tudi brat/sestra od <code>Y</code>?
+Si morda pozabil, da starša od <code>X</code> in <code>Y</code> ne smeta biti ista oseba?</p>
+<p><img src="Cousin-4.png" /></p>
+''',
+
+    'cousin_to_oneself': '''\
+<p>Kako je lahko nekdo bratranec/sestrična samemu sebi?
+Imata morda <code>X</code> in <code>Y</code> istega starša?</p>
+<p><img src="Cousin-2.png" /></p>
+''',
+
+    'cousin_need_not_be_parent': '''\
+<p>Bratranec/sestrična pravzaprav ne rabi imeti otrok...</p>
+''',
+
+#     'interesting_tidbit': '''\
+# <p>Zanimivost: nalogo bi lahko rešil tudi z uporabo rešitve za relacijo "sister".
+# Teta je namreč sestra od starša od <code>Y</code>.</p>
+# ''',
+}
+
diff --git a/prolog/problems/family_relations/descendant_2/common.py b/prolog/problems/family_relations/descendant_2/common.py
index 53320b3..9032612 100644
--- a/prolog/problems/family_relations/descendant_2/common.py
+++ b/prolog/problems/family_relations/descendant_2/common.py
@@ -13,3 +13,104 @@ descendant(X, Y) :-
   parent(Y, Z),
   descendant(X, Z).
 '''
+
+hint_type = {
+    'gender_is_irrelevant': Hint('gender_is_irrelevant'),
+    'grandparent_used': Hint('grandparent_used'),
+    'base_case': Hint('base_case'),
+    'descendant_of_oneself': Hint('ancestor_to_oneself'),
+    'descendant_need_not_be_parent': Hint('descendant_need_not_be_parent'),
+    'wrong_direction': Hint('wrong_direction'),
+}
+
+test_cases = [
+    # TODO
+]
+
+def test(program, solved_problems):
+    code = (program + '\n' +
+            server.problems.solutions_for_problems('prolog', solved_problems) + '\n' +
+            server.problems.load_facts('prolog', facts).facts)
+
+    engine_id = None
+    try:
+        engine_id, output = prolog.engine.create(code=code, timeout=1.0)
+        if not engine_id or 'error' in map(itemgetter(0), output):
+            # Engine creation failed, or syntax error in code.
+            return 0, len(test_cases)
+
+        n_correct = 0
+        for query, answers in test_cases:
+            # Limit inferences for each solution to curb unbounded recursion.
+            limited = 'call_with_inference_limit(({}), 100000, _)'.format(query)
+            if prolog.engine.check_answers(engine_id, query=limited, answers=answers, timeout=1.0):
+                n_correct += 1
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
+    passed = n_correct == len(test_cases)
+    hints = [{'id': 'test_results', 'args': {'passed': n_correct, 'total': len(test_cases)}}]
+    return passed, hints
+
+def hint(program, solved_problems):
+    tokens = prolog.util.tokenize(program)
+
+    code = (program + '\n' +
+            server.problems.solutions_for_problems('prolog', solved_problems) + '\n' +
+            server.problems.load_facts('prolog', facts).facts)
+
+    engine_id = None
+    try:
+        engine_id, output = prolog.engine.create(code=code, timeout=1.0)
+        if not engine_id:
+            raise Exception('Prolog engine failed to create.')
+
+        # gender testing is redundant
+        # this is not necessarily wrong, but worth mentioning anyway
+        targets = [prolog.util.Token('NAME', 'male'), prolog.util.Token('NAME', 'female')]
+        pos = [(t.pos, t.pos + len(t.val)) for t in tokens if t in targets]
+        if pos:
+            # TODO: resolve how highlighting info is communicated
+            return [{'id': 'gender_is_irrelevant', 'highlight': pos}]
+
+        # grandparent is a sign of complications
+        # it's likely used instead of recursion
+        targets = [prolog.util.Token('NAME', 'grandparent')]
+        pos = [(t.pos, t.pos + len(t.val)) for t in tokens if t in targets]
+        if pos:
+            # TODO: resolve how highlighting info is communicated
+            return [{'id': 'grandparent_used', 'highlight': pos}]
+
+        # missing/failed base case
+        # TODO: how will ask_truth handle/return timeouts...
+        # TODO: timeout is the same as fail in this particular case
+        if prolog.engine.ask_truth(engine_id,
+            'parent(Y, X), \+ descendant(X, Y)'):
+            return [{'id', 'base_case'}]
+
+        # descendant of oneself
+        if prolog.engine.ask_truth(engine_id, 'descendant(X, X)'):
+            return [{'id', 'descendant_of_oneself'}]
+
+        # X does not necessarily need to be a parent
+        if prolog.engine.ask_one(engine_id,
+            'descendant(X, _), \+ parent(X, _)') == 'false':
+            return [{'id': 'descendant_need_not_be_parent'}]
+
+        # ancestor instead of descendant (wrong direction)
+        # warning: knowledge base dependent
+        if prolog.engine.ask_truth(engine_id,
+            'findall(_, descendant(william, X), L1), length(L1, 6), \
+             findall(_, descendant(X, william), L2), length(L2, 2)'):
+            return [{'id', 'wrong_direction'}]
+
+    except socket.timeout as ex:
+        pass
+
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
+    return None
+
diff --git a/prolog/problems/family_relations/descendant_2/sl.py b/prolog/problems/family_relations/descendant_2/sl.py
new file mode 100644
index 0000000..fb60e76
--- /dev/null
+++ b/prolog/problems/family_relations/descendant_2/sl.py
@@ -0,0 +1,63 @@
+# coding=utf-8
+
+id = 101
+name = 'descendant/2'
+slug = 'the descendant relation'
+
+description = '''\
+<p><code>descendant(X, Y)</code>: <code>X</code> is a descendant (child, grandchild,...) of <code>Y</code>.</p>
+<pre>
+  ?- descendant(patricia, X).
+    X = william ;
+    X = tina ;
+    X = thomas.
+</pre>'''
+
+plan = ['''\
+<p>Brez rekurzije ne bo šlo... kako lahko problem prevedem na (en korak) manjši problem?</p>
+<p><img src="Descendant-3.png" /></p>
+<p>Loni naj zbriše imena relacij (parent, ancestor) s te slike!</p>
+''', '''\
+<p><img src="Descendant-3.png" /></p>
+''', '''\
+<p>Če je nek <code>Z</code> starš od <code>X</code> in je
+ta <code>Z</code> hkrati potomec od <code>Y</code>,
+potem je tudi <code>X</code> potomec od <code>Y</code>.</p>
+''']
+
+hint = {
+    'gender_is_irrelevant': '''\
+<p>Je spol res pomemben?</p>
+''',
+
+    'grandparent_used': '''\
+<p>Rešitev z "grandparent" bo premalo splošna, poskusi nadomestiti to z rekurzijo.
+Skratka, poskusi prevesti na "manjši" problem, npr. potomec v enem koraku manj
+(en korak bližji potomec)...</p>
+''',
+
+    'base_case': '''\
+<p>Si pomislil na robni pogoj? Kaj je najbolj enostaven par (potomec, prednik)?</p>
+<p><img src="Descendant-1.png" /></p>
+''',
+
+    'descendant_of_oneself': '''\
+<p>Kako je lahko nekdo potomec samega sebe?</p>
+''',
+
+    'descendant_need_not_be_parent': '''\
+<p>Potomec <code>X</code> pravzaprav ne rabi imeti otrok...</p>
+''',
+
+    'wrong_direction': '''\
+<p>Si morda sprogramiral ravno obratno in zamenjal prednika s potomcem?
+<code>X</code> naj bo potomec od <code>Y</code> in ne obratno!</p>
+''',
+
+    'interesting_tidbit': '''\
+<p>Zanimivost: nalogo bi lahko rešil tudi z uporabo rešitve za relacijo "ancestor".
+Samo obrni spremenljivki <code>X</code> in <code>Y</code>;
+če je <code>X</code> potomec od <code>Y</code>, potem je <code>Y</code> prednik od <code>X</code>.</p>
+''',
+}
+
diff --git a/prolog/problems/family_relations/father_2/common.py b/prolog/problems/family_relations/father_2/common.py
index 22c9b48..cbfbcab 100644
--- a/prolog/problems/family_relations/father_2/common.py
+++ b/prolog/problems/family_relations/father_2/common.py
@@ -74,9 +74,10 @@ def hint(program, solved_problems):
         # this hint has to be before the next two
         # as otherwise those two would always override it
         # and not convey the same (amount of) help/information
+        # warning: due to speed considerations this (48) is knowledge base dependent
+        # independent: findall(_, (parent(X, Y) ; male(X)), L2)
         if prolog.util.Token('SEMI', ';') in tokens and prolog.engine.ask_truth(engine_id,
-            'findall(_, father(X, Y), L1), length(L1, N), \
-             findall(_, (parent(X, Y) ; male(X)), L2), length(L2, N)'):
+            'findall(_, father(X, Y), L), length(L, 48)'):
             return [{'id': 'or_instead_of_and'}]
 
         # X must be male
diff --git a/prolog/problems/family_relations/grandparent_2/common.py b/prolog/problems/family_relations/grandparent_2/common.py
index 1091d52..98e40fc 100644
--- a/prolog/problems/family_relations/grandparent_2/common.py
+++ b/prolog/problems/family_relations/grandparent_2/common.py
@@ -1,8 +1,14 @@
 # coding=utf-8
 
+import socket
+import prolog.engine
+import prolog.util
+from server.hints import Hint, HintSequence
+import server.problems
+
 id = 95
 group = 'family_relations'
-number = 2
+number = 30
 visible = True
 facts = 'family_relations'
 
@@ -11,3 +17,113 @@ grandparent(X, Y) :-
   parent(X, Z),
   parent(Z, Y).
 '''
+
+hint_type = {
+    'no_common_z': Hint('no_common_z'),
+    'gender_is_irrelevant': Hint('gender_is_irrelevant'),
+    'or_instead_of_and': Hint('or_instead_of_and'),
+    'x_must_be_parent': Hint('x_must_be_parent'),
+    'x_need_not_have_parent': Hint('x_need_not_have_parent'),
+    'y_must_have_parent': Hint('y_must_have_parent'),
+    'y_need_not_be_parent': Hint('y_need_not_be_parent'),
+}
+
+test_cases = [
+    # TODO
+]
+
+def test(program, solved_problems):
+    code = (program + '\n' +
+            server.problems.solutions_for_problems('prolog', solved_problems) + '\n' +
+            server.problems.load_facts('prolog', facts).facts)
+
+    engine_id = None
+    try:
+        engine_id, output = prolog.engine.create(code=code, timeout=1.0)
+        if not engine_id or 'error' in map(itemgetter(0), output):
+            # Engine creation failed, or syntax error in code.
+            return 0, len(test_cases)
+
+        n_correct = 0
+        for query, answers in test_cases:
+            # Limit inferences for each solution to curb unbounded recursion.
+            limited = 'call_with_inference_limit(({}), 100000, _)'.format(query)
+            if prolog.engine.check_answers(engine_id, query=limited, answers=answers, timeout=1.0):
+                n_correct += 1
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
+    passed = n_correct == len(test_cases)
+    hints = [{'id': 'test_results', 'args': {'passed': n_correct, 'total': len(test_cases)}}]
+    return passed, hints
+
+def hint(program, solved_problems):
+    tokens = prolog.util.tokenize(program)
+
+    code = (program + '\n' +
+            server.problems.solutions_for_problems('prolog', solved_problems) + '\n' +
+            server.problems.load_facts('prolog', facts).facts)
+
+    engine_id = None
+    try:
+        engine_id, output = prolog.engine.create(code=code, timeout=1.0)
+        if not engine_id:
+            raise Exception('Prolog engine failed to create.')
+
+        # TODO: generic hint for:
+        # TODO: parent(X, Z1), parent(Z2, Y), Z1 = Z2
+
+        # broken "link" mistake -- no common parent/child Z
+        # warning: due to speed considerations this (1024) is knowledge base dependent
+        # independent: findall(_, (parent(X, Z1), parent(Z2, Y)), L)
+        if prolog.engine.ask_truth(engine_id,
+            'findall(_, grandparent(X, Y), L), length(L, 1024)'):
+            return [{'id': 'no_common_z'}]
+
+        # gender testing is redundant
+        # this is not necessarily wrong, but worth mentioning anyway
+        targets = [prolog.util.Token('NAME', 'male'), prolog.util.Token('NAME', 'female')]
+        pos = [(t.pos, t.pos + len(t.val)) for t in tokens if t in targets]
+        if pos:
+            # TODO: resolve how highlighting info is communicated
+            return [{'id': 'gender_is_irrelevant', 'highlight': pos}]
+
+        # OR (;) instead of AND (,)
+        # this hint has to be before the next two
+        # as otherwise those two would always override it
+        # and not convey the same (amount of) help/information
+        # warning: due to speed considerations this (64) is knowledge base dependent
+        if prolog.util.Token('SEMI', ';') in tokens and prolog.engine.ask_truth(engine_id,
+            'findall(_, grandparent(X, Y), L), length(L, 64)'):
+            return [{'id': 'or_instead_of_and'}]
+
+        # X must be a parent
+        if prolog.engine.ask_truth(engine_id,
+            'grandparent(X, _), \+ parent(X, _)'):
+            return [{'id': 'x_must_be_parent'}]
+
+        # X does not necessarily need to have a parent
+        if prolog.engine.ask_one(engine_id,
+            'grandparent(X, _), \+ parent(_, X)') == 'false':
+            return [{'id': 'x_need_not_have_parent'}]
+
+        # Y must have a parent
+        if prolog.engine.ask_truth(engine_id,
+            'grandparent(_, Y), \+ parent(_, Y)'):
+            return [{'id': 'y_must_have_parent'}]
+
+        # Y does not necessarily need to be a parent
+        if prolog.engine.ask_one(engine_id,
+            'grandparent(_, Y), \+ parent(Y, _)') == 'false':
+            return [{'id': 'y_need_not_be_parent'}]
+
+    except socket.timeout as ex:
+        pass
+
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
+    return None
+
diff --git a/prolog/problems/family_relations/grandparent_2/sl.py b/prolog/problems/family_relations/grandparent_2/sl.py
new file mode 100644
index 0000000..a26d0b7
--- /dev/null
+++ b/prolog/problems/family_relations/grandparent_2/sl.py
@@ -0,0 +1,55 @@
+# coding=utf-8
+
+id = 95
+name = 'grandparent/2'
+slug = 'X je dedek ali babica od Y'
+
+description = '''\
+<p><code>grandparent(X, Y)</code>: <code>X</code> je dedek ali babica od <code>Y</code>.</p>
+<pre>
+  ?- grandparent(tina, X).
+    X = vanessa ;
+    X = patricia.
+  ?- grandparent(tina, vanessa).
+    true.
+</pre>'''
+
+plan = ['''\
+<p><img src="Grandparent-1.png" /></p>
+<p>Loni naj zbriše imena relacij (parent, grandparent) s te slike!</p>
+''', '''\
+<p><img src="Grandparent-1.png" /></p>
+''', '''\
+<p>Če je <code>X</code> starš od starša od <code>Y</code>,
+potem je <code>X</code> stari starš od <code>Y</code>.</p>
+''']
+
+hint = {
+    'no_common_z': '''\
+<p>Si povezal <code>X</code> in <code>Y</code> preko neke skupne (iste!) osebe?</p>
+''',  # TODO: Tim, tale namig.. nisem prepričan, da mi je všeč... (kako je izražen)
+
+    'gender_is_irrelevant': '''\
+<p>Iščemo starega starša in vnuka, spol pri tem ni pomemben.</p>
+''',
+
+    'or_instead_of_and': '''\
+<p>Si morda uporabil podpičje (ki pomeni ALI) namesto vejice (ki pomeni IN)?</p>
+''',
+
+    'x_must_be_parent': '''\
+<p>Dedek ali babica ima gotovo kakšnega otroka, kajne? Torej je starš od nekoga...</p>
+''',
+
+    'x_need_not_have_parent': '''\
+<p>Starš od <code>X</code> ni pomemben, ko iščemo vnuka...</p>
+''',
+
+    'y_must_have_parent': '''\
+<p>Vnuk <code>Y</code> mora imeti starša, kajne? Ta starš pa je...</p>
+''',
+
+    'y_need_not_be_parent': '''\
+<p>Vnuk <code>Y</code> pravzaprav ne rabi imeti otrok, da ima dedka ali babico...</p>
+''',
+}
diff --git a/prolog/problems/family_relations/mother_2/common.py b/prolog/problems/family_relations/mother_2/common.py
index be0d19b..d819ef5 100644
--- a/prolog/problems/family_relations/mother_2/common.py
+++ b/prolog/problems/family_relations/mother_2/common.py
@@ -85,9 +85,10 @@ def hint(program, solved_problems):
         # this hint has to be before the next two
         # as otherwise those two would always override it
         # and not convey the same (amount of) help/information
+        # warning: due to speed considerations this (50) is knowledge base dependent
+        # independent: findall(_, (parent(X, Y) ; female(X)), L2)
         if prolog.util.Token('SEMI', ';') in tokens and prolog.engine.ask_truth(engine_id,
-            'findall(_, mother(X, Y), L1), length(L1, N), \
-             findall(_, (parent(X, Y) ; female(X)), L2), length(L2, N)'):
+            'findall(_, mother(X, Y), L), length(L, 50)'):
             return [{'id': 'or_instead_of_and'}]
 
         # X must be female
diff --git a/prolog/problems/family_relations/sister_2/common.py b/prolog/problems/family_relations/sister_2/common.py
index b3cbff0..6c48b00 100644
--- a/prolog/problems/family_relations/sister_2/common.py
+++ b/prolog/problems/family_relations/sister_2/common.py
@@ -24,7 +24,7 @@ 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'),
 }
 
@@ -118,15 +118,13 @@ def hint(program, solved_problems):
         # this is an example of using the ordering of hints for easier trigger checks
         if prolog.engine.ask_one(engine_id,
             'sister(_, Y), male(Y)') == 'false':
-            return [{'id': 'Y_can_be_of_any_gender'}]
+            return [{'id': 'y_can_be_of_any_gender'}]
 
         # X and Y must be different
         # this is the last code-specific hint (when everything else doesn't trigger anymore)
-        ans = prolog.engine.ask_one(engine_id,
-            'setof(X, (member(X, [sally, nevia, vanessa]), sister(X, X)), L), length(L, N).')
-        # TODO this barfs if ans is 'false'
-        #if ans.get('N') == '3':
-        #    return [{'id': 'x_y_must_be_different'}]
+        if 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'}]
 
         # last hints are connected with programming style
         # here, this means detecting such code:
diff --git a/prolog/problems/family_relations/sister_2/sl.py b/prolog/problems/family_relations/sister_2/sl.py
index aa66567..8c4c60f 100644
--- a/prolog/problems/family_relations/sister_2/sl.py
+++ b/prolog/problems/family_relations/sister_2/sl.py
@@ -37,7 +37,7 @@ hint = {
 <p>Sestra je navadno ženskega spola.</p>
 ''',
 
-    'Y_can_be_of_any_gender': '''\
+    'y_can_be_of_any_gender': '''\
 <p><code>Y</code> je pravzaprav lahko poljubnega spola.</p>
 ''',