Symptom: The following code would appear to run forever, since the rationals define an iterator that never quits.
QQ.list() I discovered this when I presumed that (QQ^2).list() would raise an error. It doesn't. So I patched the free module code so the iterator producing module elements would raise an error for a module over an infinite base ring. That very nearly passed all tests, except it ran afoul of the category test suite. A doctest for sets (in the Set_object_union class) constructs a vector space. To get a generic element for testing the test suite would appear to build an iterator and then grab the first element produced, so my fix broke that. (This appears to be at categories.enumerated_sets._an_element_from_iterator) It looks like structure.parent._list_from_iterator_cached is where the first examples get stuck, at least that looks like the right place when you read the code and that's part of the traceback when you use ctrl-C. Options: 1. _list_from_iterator_cached could ask if self is infinite and if so, fail. This would break the test suite too, I think. 2. The test suite framework needs to get an element by some other process. For example, (QQ^2).an_element() did not break with my patch. 3. Tough. You ought to check if a set is infinite before you try to list it (and students should just learn to do that). 4. Something else. I've attached one failure of the test suite from my patch to the module code, there were four very similar failures from the one test: _test_an_element, _test_elements, _test_elements_eq, _test_some_elements. The last error message is from my patch. I'd started this as: http://trac.sagemath.org/sage_trac/ticket/10470 I would prefer to have modules raise an error rather than just hang. If desired, I can try to fix more fundamental situations, like ZZ.list(). Comments and suggestions appreciated. Rob ~~~~~~~~~~~~ File "/sage/dev/devel/sage/sage/sets/set.py", line 864: sage: TestSuite(X).run() Expected nothing Got: Failure in _test_an_element: Traceback (most recent call last): File "/sage/dev/local/lib/python/site-packages/sage/misc/ sage_unittest.py", line 275, in run test_method(tester = tester) File "/sage/dev/local/lib/python/site-packages/sage/categories/ sets_cat.py", line 353, in _test_an_element an_element = self.an_element() File "/sage/dev/local/lib/python/site-packages/sage/misc/ cachefunc.py", line 322, in __call__ return self._cachedmethod._instance_call(self._instance, *args, **kwds) File "/sage/dev/local/lib/python/site-packages/sage/misc/ cachefunc.py", line 466, in _instance_call cache[key] = self._cachedfunc.f(inst, *args, **kwds) File "/sage/dev/local/lib/python/site-packages/sage/categories/ enumerated_sets.py", line 441, in _an_element_from_iterator return it.next() File "/sage/dev/local/lib/python/site-packages/sage/sets/ set.py", line 939, in __iter__ for x in self.__X: File "/sage/dev/local/lib/python/site-packages/sage/modules/ free_module.py", line 1046, in __iter__ raise ValueError("module's base ring, or vector space's field, is not finite, so cannot iterate over elements") ValueError: module's base ring, or vector space's field, is not finite, so cannot iterate over elements -- To post to this group, send an email to sage-devel@googlegroups.com To unsubscribe from this group, send an email to sage-devel+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-devel URL: http://www.sagemath.org
