3 files changed, 80 insertions, 0 deletions
diff --git a/prolog/problems/lists_advanced/count_3/common.py b/prolog/problems/lists_advanced/count_3/common.py
new file mode 100644
index 0000000..2953f06
--- /dev/null
+++ b/prolog/problems/lists_advanced/count_3/common.py
@@ -0,0 +1,54 @@
+# coding=utf-8
+
+from operator import itemgetter
+import prolog.engine
+import server.problems
+
+id = 120
+number = 27
+visible = False
+facts = None
+
+solution = '''\
+count(_, [], 0).
+count(X, [X|T], N) :-
+  count(X, T, NT),
+  N is NT + 1.
+count(X, [Y|T], NT) :-
+  X \== Y,
+  count(X, T, NT).
+'''
+
+test_cases = [
+    ('count(a, [], X)',
+        [{'X': '0'}]),
+    ('count(r, [a, r, b, c, r], X)',
+        [{'X': '2'}]),
+    ('count(l, [l, l, l, 1, 2, 3], X)',
+        [{'X': '3'}]),
+    ('count(z, [a, b, c, z, z], X)',
+        [{'X': '2'}]),
+]
+
+def test(code, aux_code):
+    n_correct = 0
+    engine_id = None
+    try:
+        engine_id, output = prolog.engine.create(code=code+aux_code, timeout=1.0)
+        if engine_id is not None and 'error' not in map(itemgetter(0), output):
+            # Engine successfully created, and no syntax error in program.
+            for query, answers in test_cases:
+                if prolog.engine.check_answers(engine_id, query=query, answers=answers, timeout=1.0):
+                    n_correct += 1
+    except socket.timeout:
+        pass
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
+    hints = [{'id': 'test_results', 'args': {'passed': n_correct, 'total': len(test_cases)}}]
+    return n_correct, len(test_cases), hints
+
+def hint(code, aux_code):
+    # TODO
+    return []
diff --git a/prolog/problems/lists_advanced/count_3/en.py b/prolog/problems/lists_advanced/count_3/en.py
new file mode 100644
index 0000000..dd13bc0
--- /dev/null
+++ b/prolog/problems/lists_advanced/count_3/en.py
@@ -0,0 +1,13 @@
+# coding=utf-8
+
+name = 'count/3'
+slug = 'find the number of occurrences of an element in list'
+
+description = '''\
+<p><code>count(X, L, N)</code>: <code>N</code> is the number of times the element <code>X</code> appears in the list <code>L</code>.</p>
+<pre>
+?- count(1, [1,2,1,3,1], N).
+  N = 3.
+</pre>'''
+
+hint = {}
diff --git a/prolog/problems/lists_advanced/count_3/sl.py b/prolog/problems/lists_advanced/count_3/sl.py
new file mode 100644
index 0000000..98cd6f8
--- /dev/null
+++ b/prolog/problems/lists_advanced/count_3/sl.py
@@ -0,0 +1,13 @@
+# coding=utf-8
+
+name = 'count/3'
+slug = 'Preštej kolikokrat se element pojavi v seznamu'
+
+description = '''\
+<p><code>count(X, L, N)</code>: <code>N</code> je število kolikokrat se element <code>X</code> pojavi v seznamu <code>L</code>.</p>
+<pre>
+?- count(1, [1,2,1,3,1], N).
+  N = 3.
+</pre>'''
+
+hint = {}