From df8c0b864281e448498cc244cac8fdcf985b373c Mon Sep 17 00:00:00 2001
From: Timotej Lazar <timotej.lazar@fri.uni-lj.si>
Date: Sat, 19 Mar 2016 10:05:37 +0100
Subject: Prolog: add triggers for evenlen+oddlen hints

---
 .../lists_advanced/evenlen_1_+_oddlen_1/common.py  | 26 +++++++++++++++++++++-
 .../lists_advanced/evenlen_1_+_oddlen_1/sl.py      | 16 +++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

(limited to 'prolog/problems')

diff --git a/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/common.py b/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/common.py
index 828b742..3b997dd 100644
--- a/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/common.py
+++ b/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/common.py
@@ -25,6 +25,10 @@ hint_type = {
     'eq_instead_of_equ': Hint('eq_instead_of_equ'),
     'predicate_always_false': Hint('predicate_always_false'),
     'base_case': Hint('base_case'),
+    'extra_base_case': Hint('extra_base_case'),
+    'arbitrary_base_case': Hint('arbitrary_base_case'),
+    'arithmetics_used': Hint('arithmetics_used'),
+    'odd_and_even_mixed_up': Hint('odd_and_even_mixed_up'),
     'recursive_case': Hint('recursive_case'),
     'timeout': Hint('timeout'),
 }
@@ -76,9 +80,29 @@ def hint(code, aux_code):
                    [{'id': 'eq_instead_of_equ'}]
 
         # missing/failed base case
-        if not prolog.engine.ask_truthTO(engine_id, 'evenlen([]), oddlen([a])'):
+        if not prolog.engine.ask_truthTO(engine_id, 'evenlen([])'):
             return [{'id': 'base_case'}]
 
+        # redundant base case when evenlen and oddlen call each other
+        if prolog.engine.ask_truthTO(engine_id,
+                'findall(q, (oddlen([a, b, c, d, e]) ; evenlen([a, b, c, d, e, f])), [q, q, q, q])'):
+            return [{'id': 'extra_base_case'}]
+
+        # arbitrary base case
+        if prolog.engine.ask_truthTO(engine_id,
+                'evenlen(qQ), evenlen(parent(X, q)) ; oddlen(qQ), oddlen(parent(X, q))'):
+            return [{'id': 'arbitrary_base_case'}]
+
+        # arithmetics used
+        if any(t.val in ('is', 'len', 'length') for t in tokens):
+            return [{'id': 'arithmetics_used'}]
+
+        # odd and even mixed up
+        # TODO base_case will typically fire first when this is true
+        if prolog.engine.ask_truthTO(engine_id,
+                'oddlen([]), evenlen([q]), ! ; oddlen([q, q]), evenlen([q, q, q])'):
+            return [{'id': 'odd_and_even_mixed_up'}]
+
         # target predicate seems to always be false
         if not prolog.engine.ask_truthTO(engine_id, 'evenlen(_) ; oddlen(_)'):
             return [{'id': 'predicate_always_false'}]
diff --git a/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/sl.py b/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/sl.py
index d56cc10..8600c55 100644
--- a/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/sl.py
+++ b/prolog/problems/lists_advanced/evenlen_1_+_oddlen_1/sl.py
@@ -29,6 +29,22 @@ implicitno že kar v argumentih predikata (glavi stavka).</p>
     'base_case': '''\
 <p>Si pomislil na robni pogoj? Kaj je najbolj enostaven primer, ko je element v seznamu?
 Do katerega elementa najlažje prideš?</p>
+''',
+
+    'extra_base_case': '''\
+<p>extra_base_case</p>
+''',
+
+    'arbitrary_base_case': '''\
+<p>arbitrary_base_case</p>
+''',
+
+    'arithmetics_used': '''\
+<p>arithmetics_used</p>
+''',
+
+'odd_and_even_mixed_up': '''\
+<p>odd_and_even_mixed_up</p>
 ''',
 
     'recursive_case': '''\
-- 
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