From 820e032e90b31507c4084148a099a0a159e01583 Mon Sep 17 00:00:00 2001
From: Aleksander Sadikov <aleksander.sadikov@fri.uni-lj.si>
Date: Mon, 14 Mar 2016 16:28:57 +0100
Subject: Plans for divide/3 added.

---
 prolog/problems/lists/divide_3/common.py | 46 ++++++++++++++++++++++----------
 1 file changed, 32 insertions(+), 14 deletions(-)

(limited to 'prolog/problems/lists/divide_3/common.py')

diff --git a/prolog/problems/lists/divide_3/common.py b/prolog/problems/lists/divide_3/common.py
index 544dbc4..34b7fe9 100644
--- a/prolog/problems/lists/divide_3/common.py
+++ b/prolog/problems/lists/divide_3/common.py
@@ -8,7 +8,7 @@ from server.hints import Hint, HintPopup
 import server.problems
 
 id = 115
-number = 8
+number = 7
 visible = True
 facts = None
 
@@ -26,8 +26,10 @@ hint_type = {
     'base_case': Hint('base_case'),
     'recursive_case': Hint('recursive_case'),
     'timeout': Hint('timeout'),
-    '[]_should_not_succeed': Hint('[]_should_not_succeed'),
-    'list_returned': Hint('list_returned'),
+    '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 = [
@@ -76,28 +78,44 @@ def hint(code, aux_code):
             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
 
-        # succeeds when asked to return the last element of an empty list
-        if prolog.engine.ask_truthTO(engine_id, 'last_elem([], _)'):
-            return [{'id': '[]_should_not_succeed'}]
 
-        # returns a list, not an element as required
-        if prolog.engine.ask_one(engine_id, 'last_elem([qQ], [qQ])'):  # 'last_elem([qQ], X), is_list(X)' with ask_one?
-            return [{'id': 'list_returned'}]
+        # 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], [yowza,cob], [brix]), 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_truthTO(engine_id, 'last_elem([], [], [])'):
+        if not prolog.engine.ask_truthTO(engine_id, 'divide([], [], [])'):
             return [{'id': 'base_case'}]
 
         # target predicate seems to always be false
-        if not prolog.engine.ask_truthTO(engine_id, 'last_elem(_, _)') and \
-           not prolog.engine.ask_truthTO(engine_id, 'last_elem([_,_,_,_,_,_], _)'):
+        if not prolog.engine.ask_truthTO(engine_id, 'divide([_,_,_,_,_], _, _)') and \
+           not prolog.engine.ask_truthTO(engine_id, 'divide([_,_,_,_,_,_], _, _)'):
             return [{'id': 'predicate_always_false'}]
 
-        # base case works, the recursive doesn't (but it doesn't timeout)
+        # 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, 'last_elem([qa,qb,qQ,qc], qc)'):
+        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:
-- 
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