From 3ed1137118bf719eab1d3fc1d230441057cdf854 Mon Sep 17 00:00:00 2001
From: Aleksander Sadikov <aleksander.sadikov@fri.uni-lj.si>
Date: Mon, 14 Mar 2016 17:22:11 +0100
Subject: Basics for permute/2 added.

---
 prolog/problems/lists/permute_2/common.py | 77 ++++++++++++++++++++++++++++++-
 1 file changed, 76 insertions(+), 1 deletion(-)

(limited to 'prolog/problems/lists/permute_2/common.py')

diff --git a/prolog/problems/lists/permute_2/common.py b/prolog/problems/lists/permute_2/common.py
index e39300b..3035159 100644
--- a/prolog/problems/lists/permute_2/common.py
+++ b/prolog/problems/lists/permute_2/common.py
@@ -2,6 +2,9 @@
 
 from operator import itemgetter
 import prolog.engine
+import prolog.util
+import socket
+from server.hints import Hint, HintPopup
 import server.problems
 
 id = 107
@@ -19,6 +22,19 @@ permute(L, [X|P]) :-
   permute(L1, P).
 '''
 
+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'),
+    'base_case_arbitrary': Hint('base_case_arbitrary'),
+    'second_base_case_missing': Hint('second_base_case_missing'),
+    'unsuccessful_conc_use': Hint('unsuccessful_conc_use'),
+    'forcing_result_onto_recursion': Hint('forcing_result_onto_recursion'),
+}
+
 test_cases = [
     ('permute([], X)',
         [{'X': '[]'}]),
@@ -48,5 +64,64 @@ 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'}]
+
+        # general unsuccessful use of conc (not appropriate for this exercise)
+        if prolog.util.Token('NAME', 'conc') in tokens:
+            return [{'id': 'unsuccessful_conc_use'}]
+
+        # recursion is getting bigger and bigger
+
+
+        # forcing result onto recursion; case of divide(T, [H1|L1], [H2|L2])
+        if not prolog.engine.ask_truthTO(engine_id, 'divide([a,b,c], _, _)') and \
+           prolog.engine.ask_truthTO(engine_id,
+           'asserta( divide([cob], [yowza,cob], [brix]) ), divide([yowza,brix,cob], [cob], []), retract( divide([cob], [yowza,cob], [brix]) )'):
+            return [{'id': 'forcing_result_onto_recursion'}]
+
+        # base case succeeds with arbitrary result
+        if prolog.engine.ask_truthTO(engine_id, 'divide([], L1, L2), (var(L1) ; var(L2))') or \
+           prolog.engine.ask_truthTO(engine_id, 'divide([q], L1, L2), (var(L1) ; var(L2))') or \
+           prolog.engine.ask_truthTO(engine_id, 'divide([q], [q|L1], L2), (var(L1) ; var(L2))'):
+            return [{'id': 'base_case_arbitrary'}]
+
+        # one base case ok, the other one is missing (or bad)
+        # only trigger when recursion also works, because that makes more sense to the student
+        # than immediately telling him or her that there is another base case missing
+        if prolog.engine.ask_truthTO(engine_id,
+           'divide([a,b], [a], [b]), \+ divide([a,b,c], [a,c], [b]) ; \+ divide([a,b], [a], [b]), divide([a,b,c], [a,c], [b])'):
+            return [{'id': 'second_base_case_missing'}]
+
+        # missing/failed base case
+        if not prolog.engine.ask_truth(engine_id, 'divide([], [], [])'):
+            return [{'id': 'base_case'}]
+
+#        # target predicate seems to always be false
+#        if not prolog.engine.ask_truthTO(engine_id, 'divide([_,_,_,_,_], _, _)') and \
+#           not prolog.engine.ask_truthTO(engine_id, 'divide([_,_,_,_,_,_], _, _)'):
+#            return [{'id': 'predicate_always_false'}]
+
+        # base cases work, 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, 'divide([qa,qb,qc,qd], [qa,qc], [qb,qd])'):
+            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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