1 files changed, 51 insertions, 5 deletions
diff --git a/python/problems/introduction/fahrenheit_to_celsius/common.py b/python/problems/introduction/fahrenheit_to_celsius/common.py
index 34f2832..076d322 100644
--- a/python/problems/introduction/fahrenheit_to_celsius/common.py
+++ b/python/problems/introduction/fahrenheit_to_celsius/common.py
@@ -22,18 +22,26 @@ hint_type = {
 def test(python, code):
     # List of inputs: (expression to eval, stdin).
     test_in = [
-        (None, '0\n'),
-        (None, '100\n'),
+        (None, '32\n'),
+        (None, '212\n'),
+        (None, '-459.4\n'),
+        (None, '98.6\n'),
+        (None, '1832\n'),
     ]
     test_out = [
-        '-17.7',
-        '37.7',
+        '0',
+        '100',
+        '-273',
+        '37',
+        '1000'
     ]
 
     # List of outputs: (expression result, stdout, stderr, exception).
     answers = python(code=code, inputs=test_in, timeout=1.0)
     outputs = [ans[1] for ans in answers]
 
+    print (answers)
+
     n_correct = 0
     for output, correct in zip(outputs, test_out):
         if correct in output:
@@ -41,8 +49,46 @@ def test(python, code):
     return n_correct, len(test_in)
 
 def hint(python, code):
-    if not code:
+    # run one test first to see if there are any exceptions
+    test_in = [(None, '212\n')]
+    exc = python(code=code, inputs=test_in, timeout=1.0)[0][3]
+    # have an exception!
+    if exc:
+        if 'NameError' in exc:
+            return [{'id':'name_error'}]
+        if 'not callable' in exc:
+            return [{'id':'not_callable'}]
+        if 'unsupported operand' in exc:
+            return [{'id':'unsupported_operand'}]
+        if 'SyntaxError' in exc:
+            return [{'id':'syntax_error'}]
+        if 'IndentationError' in exc:
+            return [{'id':'indentation_error'}]
+
+
+    # the trick is to decide when to show the plan and when the first hint. 
+    # I implemented a simple idea: show plan, when code contains something from the 
+    # solution, but not input. 
+    if not code or (not has_token_sequence(code, ['input']) and 
+                    (has_token_sequence(code, ['32']) or 
+                     has_token_sequence(code, ['=', '5']) or 
+                     has_token_sequence(code, ['print']))):
         return [{'id': 'plan'}]
+
+
+    # if input is not present in code, student needs to learn about input
     if not has_token_sequence(code, ['input']):
         return [{'id': 'no_input_call'}]
+
+    # if tokens * or / or = are not in code, we have to teach them how to 
+    # evaluate expressions.
+    if (not has_token_sequence(code, ['/']) or
+        not has_token_sequence(code, ['*']) or
+        not has_token_sequence(code, ['='])):
+        return [{'id' : 'expressions_python'}]
+
+    # student is not using print function
+    if not has_token_sequence(code, ['print']):
+        return [{'id' : 'printing'}]
+
     return None