#16707: Provide more useful error messages from categories
--------------------------+----------------------------
Reporter: ppurka | Owner:
Type: defect | Status: new
Priority: major | Milestone: sage-6.3
Component: categories | Keywords:
Merged in: | Authors:
Reviewers: | Report Upstream: N/A
Work issues: | Branch:
Commit: | Dependencies:
Stopgaps: |
--------------------------+----------------------------
The reason for opening this ticket is well discussed in #16644 (see
@vbraun's comments). Essentially, things like this should not happen.
Here is a file called `a.sage`.
{{{#!python
import sage.modules.module as module
class MyClass(module.Module):
def __init__(self, number):
base_ring = number.parent()
module.Module.__init__(self, base_ring)
}}}
And here is an output. This should not happen at all.
{{{
sage: %runfile a.sage
sage: C = MyClass(1)
sage: C.element_class()
---------------------------------------------------------------------------
AttributeError Traceback (most recent call
last)
<ipython-input-3-66b2e3babdf7> in <module>()
----> 1 C.element_class()
/home/punarbasu/tmp/sage/local/lib/python2.7/site-
packages/sage/structure/parent.so in
sage.structure.parent.Parent.__getattr__
(build/cythonized/sage/structure/parent.c:7290)()
/home/punarbasu/tmp/sage/local/lib/python2.7/site-
packages/sage/structure/misc.so in
sage.structure.misc.getattr_from_other_class
(build/cythonized/sage/structure/misc.c:1687)()
AttributeError: 'MyClass_with_category' object has no attribute
'element_class'
sage: 'element_class' in dir(C)
True
sage: hasattr(C, 'element_class')
False
}}}
There are other cases where it is not clear why some stuff is not
implemented and yet available in the method list:
{{{
sage: C.sum(())
---------------------------------------------------------------------------
NotImplementedError Traceback (most recent call
last)
...
NotImplementedError:
}}}
So, this ticket should go through all the default methods that are usually
available and provide useful error message - for instance the `sum` method
can say that the `zero()` method needs to be implemented.
If the changes are extensive, then open other child tickets and put them
in the "dependencies" of this one.
--
Ticket URL: <http://trac.sagemath.org/ticket/16707>
Sage <http://www.sagemath.org>
Sage: Creating a Viable Open Source Alternative to Magma, Maple, Mathematica,
and MATLAB
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