diff --git a/aprendizations/questions.py b/aprendizations/questions.py
index 474860a..62fc9d3 100644
--- a/aprendizations/questions.py
+++ b/aprendizations/questions.py
@@ -42,7 +42,6 @@ class Question(dict):
             'comments': '',
             'solution': '',
             'files': {},
-            # 'max_tries': 3,
             }))
 
     def correct(self) -> None:
@@ -220,13 +219,19 @@ class QuestionCheckbox(Question):
         # check grade boundaries
         if self['discount'] and not all(0.0 <= x <= 1.0
                                         for x in self['correct']):
-            logger.warning('          * * *  BEHAVIOR CHANGE NOTICE  * * *')
-            msg = (f'Correct values must be in the interval [0.0, 1.0] in '
-                   f'"{self["ref"]}"')
-            logger.warning(msg)
-            logger.warning('I will convert "correct" to the new behavior, but '
-                           'you should change it in the questions')
-            logger.warning('          * * *  END OF NOTICE           * * *')
+
+            msg0 = ('+-------------- BEHAVIOR CHANGE NOTICE --------------+')
+            msg1 = ('| Correct values must be in the interval [0.0, 1.0]. |')
+            msg2 = ('| I will convert to the new behavior, but you should |')
+            msg3 = ('| fix it in the question.                            |')
+            msg4 = ('+----------------------------------------------------+')
+            logger.warning(msg0)
+            logger.warning(msg1)
+            logger.warning(msg2)
+            logger.warning(msg3)
+            logger.warning(msg4)
+            logger.warning(f'please fix "{self["ref"]}"')
+
             # normalize to [0,1]
             self['correct'] = [(x+1)/2 for x in self['correct']]
 
@@ -296,15 +301,21 @@ class QuestionText(Question):
 
         # make sure its always a list of possible correct answers
         if not isinstance(self['correct'], list):
-            self['correct'] = [self['correct']]
+            self['correct'] = [str(self['correct'])]
+        else:
+            # make sure all elements of the list are strings
+            self['correct'] = [str(a) for a in self['correct']]
 
-        # make sure all elements of the list are strings
-        self['correct'] = [str(a) for a in self['correct']]
+        for f in self['transform']:
+            if f not in ('remove_space', 'trim', 'normalize_space', 'lower',
+                         'upper'):
+                msg = (f'Unknown transform "{f}" in "{self["ref"]}"')
+                raise QuestionException(msg)
 
-        # make sure that the answers are invariant with respect to the filters
+        # check if answers are invariant with respect to the transforms
         if any(c != self.transform(c) for c in self['correct']):
             logger.warning(f'in "{self["ref"]}", correct answers are not '
-                           'invariant wrt transformations')
+                           'invariant wrt transformations => never correct')
 
     # ------------------------------------------------------------------------
     # apply optional filters to the answer
@@ -358,8 +369,12 @@ class QuestionTextRegex(Question):
         if not isinstance(self['correct'], list):
             self['correct'] = [self['correct']]
 
-        # make sure all elements of the list are strings
-        self['correct'] = [str(a) for a in self['correct']]
+        # converts patterns to compiled versions
+        try:
+            self['correct'] = [re.compile(a) for a in self['correct']]
+        except Exception:
+            msg = f'Failed to compile regex in "{self["ref"]}"'
+            raise QuestionException(msg)
 
     # ------------------------------------------------------------------------
     def correct(self) -> None:
@@ -368,12 +383,12 @@ class QuestionTextRegex(Question):
             self['grade'] = 0.0
             for r in self['correct']:
                 try:
-                    if re.match(r, self['answer']):
+                    if r.match(self['answer']):
                         self['grade'] = 1.0
                         return
                 except TypeError:
-                    logger.error(f'While matching regex {self["correct"]} with'
-                                 f' answer "{self["answer"]}".')
+                    logger.error(f'While matching regex {r.pattern} with '
+                                 f'answer "{self["answer"]}".')
 
 
 # ============================================================================
@@ -395,6 +410,30 @@ class QuestionNumericInterval(Question):
             'correct': [1.0, -1.0],   # will always return false
             }))
 
+        # if only one number n is given, make an interval [n,n]
+        if isinstance(self['correct'], (int, float)):
+            self['correct'] = [float(self['correct']), float(self['correct'])]
+
+        # make sure its a list of two numbers
+        elif isinstance(self['correct'], list):
+            if len(self['correct']) != 2:
+                msg = (f'Numeric interval must be a list with two numbers, in '
+                       f'{self["ref"]}')
+                raise QuestionException(msg)
+
+            try:
+                self['correct'] = [float(n) for n in self['correct']]
+            except Exception:
+                msg = (f'Numeric interval must be a list with two numbers, in '
+                       f'{self["ref"]}')
+                raise QuestionException(msg)
+
+        # invalid
+        else:
+            msg = (f'Numeric interval must be a list with two numbers, in '
+                   f'{self["ref"]}')
+            raise QuestionException(msg)
+
     # ------------------------------------------------------------------------
     def correct(self) -> None:
         super().correct()
@@ -576,7 +615,7 @@ class QFactory(object):
         if q['type'] == 'generator':
             logger.debug(f' \\_ Running "{q["script"]}".')
             q.setdefault('args', [])
-            q.setdefault('stdin', '')  # FIXME is it really necessary?
+            q.setdefault('stdin', '')
             script = path.join(q['path'], q['script'])
             out = await run_script_async(script=script, args=q['args'],
                                          stdin=q['stdin'])
--
libgit2 0.21.2