From c1cc16c4088cb68d205342450493957f17a71c9a Mon Sep 17 00:00:00 2001
From: Timotej Lazar <timotej.lazar@fri.uni-lj.si>
Date: Thu, 17 Mar 2016 15:41:44 +0100
Subject: Prolog: add generic recursion hints for lists_advanced problems

TODO modify texts in */sl.py where appropriate.
---
 prolog/problems/lists_advanced/min_2/common.py | 50 +++++++++++++++++++++++---
 1 file changed, 46 insertions(+), 4 deletions(-)

(limited to 'prolog/problems/lists_advanced/min_2/common.py')

diff --git a/prolog/problems/lists_advanced/min_2/common.py b/prolog/problems/lists_advanced/min_2/common.py
index 213da5a..ec0ccd2 100644
--- a/prolog/problems/lists_advanced/min_2/common.py
+++ b/prolog/problems/lists_advanced/min_2/common.py
@@ -1,8 +1,9 @@
-# coding=utf-8
-
 from operator import itemgetter
+import socket
+
 import prolog.engine
-import server.problems
+import prolog.util
+from server.hints import Hint, HintPopup
 
 id = 108
 number = 15
@@ -18,6 +19,15 @@ min([H|T], Min):-
     H >= Min1, Min is Min1 ).
 '''
 
+hint_type = {
+    'eq_instead_of_equ_markup': HintPopup('eq_instead_of_equ_markup'),
+    'eq_instead_of_equ': Hint('eq_instead_of_equ'),
+    'predicate_always_false': Hint('predicate_always_false'),
+    'base_case': Hint('base_case'),
+    'recursive_case': Hint('recursive_case'),
+    'timeout': Hint('timeout'),
+}
+
 test_cases = [
     ('min([15], X)',
         [{'X': '15'}]),
@@ -49,5 +59,37 @@ def test(code, aux_code):
     return n_correct, len(test_cases), hints
 
 def hint(code, aux_code):
-    # TODO
+    tokens = prolog.util.tokenize(code)
+
+    try:
+        engine_id, output = prolog.engine.create(code=code+aux_code, timeout=1.0)
+
+        # strict equality testing instead of simple matching
+        # this is usually (but not necessarily) wrong
+        targets = [prolog.util.Token('EQ', '==')]
+        marks = [(t.pos, t.pos + len(t.val)) for t in tokens if t in targets]
+        if marks:
+            return [{'id': 'eq_instead_of_equ_markup', 'start': m[0], 'end': m[1]} for m in marks] + \
+                   [{'id': 'eq_instead_of_equ'}]
+
+        # missing/failed base case
+        if not prolog.engine.ask_truthTO(engine_id, 'min([-45], 45)'):
+            return [{'id': 'base_case'}]
+
+        # target predicate seems to always be false
+        if not prolog.engine.ask_truthTO(engine_id, 'min(_, _)'):
+            return [{'id': 'predicate_always_false'}]
+
+        # base case works, the recursive doesn't (but it doesn't timeout)
+        # this may be left as the last, most generic hint
+        if not prolog.engine.ask_truth(engine_id, 'min([2, 41, -22], -22)'):
+            return [{'id': 'recursive_case'}]
+
+    except socket.timeout as ex:
+        return [{'id': 'timeout'}]
+
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
     return []
-- 
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