Reordering the exercises in list chapter #1.

1 files changed, 73 insertions, 3 deletions

diff --git a/prolog/problems/lists/insert_3/common.py b/prolog/problems/lists/insert_3/common.py
index be4da78..5b049f7 100644
--- a/prolog/problems/lists/insert_3/common.py
+++ b/prolog/problems/lists/insert_3/common.py
@@ -2,11 +2,14 @@
 
 from operator import itemgetter
 import prolog.engine
+import prolog.util
+import socket
+from server.hints import Hint, HintPopup
 import server.problems
 
 id = 106
-number = 13
-visible = False
+number = 1
+visible = True
 facts = None
 
 solution = '''\
@@ -17,6 +20,18 @@ insert(X, List, BigList) :-
   del106(X, BigList, List).
 '''
 
+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'),
+    'timeout': Hint('timeout'),
+    'del_from_empty_list_success': Hint('del_from_empty_list_success'),
+    'lost_heads': Hint('lost_heads'),
+    'recursive_case': Hint('recursive_case'),
+    'leading_heads_all_x': Hint('leading_heads_all_x'),
+}
+
 test_cases = [
     ('insert(l, [], X)',
         [{'X': '[l]'}]),
@@ -46,5 +61,60 @@ 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'}]
+
+        # recursion is getting bigger and bigger
+
+
+        # deleting from empty list succeeds with an emtpy list result
+        if prolog.engine.ask_truthTO(engine_id, 'del(_, [], _)'):
+            return [{'id': 'del_from_empty_list_success'}]
+
+        # missing/failed base case
+        if not prolog.engine.ask_one(engine_id, 'del(qQ, [qQ,qa,qb,qc], [qa,qb,qc])'):
+            return [{'id': 'base_case'}]
+
+        # target predicate seems to always be false
+        if not prolog.engine.ask_truth(engine_id, 'del(_, [_,_,_,_,_,_], _)'):
+            return [{'id': 'predicate_always_false'}]
+
+        # forgot to put list head(s) back in the list when deleting an element
+        if prolog.engine.ask_truth(engine_id, 'del(q, [a,b,c,d,q,x,y,z], [x,y,z])'):
+            return [{'id': 'lost_heads'}]
+
+        # used [X|T] instead of more general [H|T] in recursive case
+        if prolog.engine.ask_truth(engine_id, \
+                'findall(NL, del(q, [q,q,q,a,b,c], NL), [[q,q,a,b,c],[q,q,a,b,c],[q,q,a,b,c]]).') and \
+           not prolog.engine.ask_truth(engine_id, 'del(q, [a,b,c,q,x,y,z], [a,b,c,x,y,z])'):
+            return [{'id': 'leading_heads_all_x'}]
+
+        # L=[H|T] at the end of the rule; this can be detected with test cases and can be wrong (in some sense)
+        # TODO: implement it, and provide a good explanation (might be hard)
+
+        # 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, 'del(qQ, [qa,qb,qQ,qc], [qa,qb,qc])'):
+            return [{'id': 'recursive_case'}]
+
+
+    except socket.timeout as ex:
+        return [{'id': 'timeout'}]
+
+    finally:
+        if engine_id:
+            prolog.engine.destroy(engine_id)
+
     return []
+
+# https://xkcd.com/323/
\ No newline at end of file