From 876801eeff57b10d87a25d2ffaab338dc915dbdd Mon Sep 17 00:00:00 2001
From: Aleksander Sadikov <aleksander.sadikov@fri.uni-lj.si>
Date: Sat, 12 Mar 2016 00:49:44 +0100
Subject: Hints for conc/3 added.

---
 prolog/problems/lists/conc_3/common.py | 29 +++++++++++++++++++++++++----
 1 file changed, 25 insertions(+), 4 deletions(-)

(limited to 'prolog/problems/lists/conc_3/common.py')

diff --git a/prolog/problems/lists/conc_3/common.py b/prolog/problems/lists/conc_3/common.py
index 3ed35bc..fd97865 100644
--- a/prolog/problems/lists/conc_3/common.py
+++ b/prolog/problems/lists/conc_3/common.py
@@ -26,6 +26,10 @@ hint_type = {
     'timeout': Hint('timeout'),
     'final_hint': Hint('final_hint'),
     'second_list_iteration': Hint('second_list_iteration'),
+    'forcing_result_onto_recursion': Hint('forcing_result_onto_recursion'),
+    'two_heads_markup': HintPopup('two_heads_markup'),
+    'two_heads': Hint('two_heads'),
+    'insertion_into_second_list': Hint('insertion_into_second_list'),
 }
 
 test_cases = [
@@ -77,15 +81,32 @@ def hint(code, aux_code):
         # recursion is getting bigger and bigger
 
 
-#        # missing/failed base case
-#        if not prolog.engine.ask_truthTO(engine_id, 'conc([], [qa,qb,qc], [qa,qb,qc])'):
-#            return [{'id': 'base_case'}]
-
         # shortening the second list instead of first list
         if prolog.engine.ask_truthTO(engine_id,
            'conc([a,b,c], [1,2,3,4], L), (L = [1,2,3,4,a,b,c] ; L = [4,3,2,1,a,b,c])'):
             return [{'id': 'second_list_iteration'}]
 
+        # inserting first list's head into the second list in recursive call: conc(T, [H\L2], L)
+        if prolog.engine.ask_truthTO(engine_id,
+           'conc([a,b,c,d,e], [1,2,3,4], L = [e,d,c,b,a,1,2,3,4])'):
+            return [{'id': 'insertion_into_second_list'}]
+
+        # forcing result onto recursion; case of conc(T, L2, [H|L])
+        if not prolog.engine.ask_truthTO(engine_id, 'conc([a,b,c,d,e], _, _)') and \
+           prolog.engine.ask_truthTO(engine_id,
+           'asserta( conc([b,c],[1,2],[yowza,b,c,1,2]) ), conc([yowza,b,c],[1,2],L), retract( conc([b,c],[1,2],[yowza,b,c,1,2]) )'):
+            return [{'id': 'forcing_result_onto_recursion'}]
+
+        # using two heads indicating that the user wants heads from both lists
+        # TODO: Tim, it would be nice/safer to catch this just for a single clause, not whole code.
+        if prolog.util.Token('NAME', 'H1') in tokens and \
+           (prolog.util.Token('NAME', 'H') in tokens or prolog.util.Token('NAME', 'H2') in tokens):
+            targets = [prolog.util.Token('NAME', 'H1'), prolog.util.Token('NAME', 'H2')]
+            marks = [(t.pos, t.pos + len(t.val)) for t in tokens if t in targets]
+            if marks:
+                return [{'id': 'two_heads_markup', 'start': m[0], 'end': m[1]} for m in marks] + \
+                       [{'id': 'two_heads'}]
+
         # missing/failed base case
         if not prolog.engine.ask_one(engine_id, 'conc([], [qa,qb,qc], [qa,qb,qc])'):
             return [{'id': 'base_case'}]
-- 
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