#5756: improve coverage of rings/morphism.pyx
-------------------------+--------------------------------------------------
Reporter: was | Owner: mabshoff
Type: enhancement | Status: new
Priority: major | Milestone: sage-3.4.1
Component: doctest | Keywords:
-------------------------+--------------------------------------------------
Old description:
> BUGS FOUND:
>
> 1. bug in __cmp__
> {{{
> 10:56 < wstein-5756> Wow, I was reading the __cmp__ for ring lifting
> maps.
> 10:56 < wstein-5756> Check out this bug:
> 10:56 < wstein-5756> Zmod(8).lift() == Zmod(10).lift()
> 10:56 < wstein-5756> True
> 10:56 < wstein-5756> Any two lifting maps are always equal.
> 10:56 < wstein-5756> Ouch.
> }}}
>
> 2. Another bug related to __cmp__: #5758 (weird "hello")
New description:
Fix the coverage of morphism.pyx, which is bad.
--
Comment(by was):
BUGS FOUND:
1. bug in __cmp__
{{{
10:56 < wstein-5756> Wow, I was reading the __cmp__ for ring lifting maps.
10:56 < wstein-5756> Check out this bug:
10:56 < wstein-5756> Zmod(8).lift() == Zmod(10).lift()
10:56 < wstein-5756> True
10:56 < wstein-5756> Any two lifting maps are always equal.
10:56 < wstein-5756> Ouch.
}}}
2. Another bug related to __cmp__: #5758 (weird "hello")
3. __nonzero__ is wrong for ring morphisms, since Sage does have the 0
ring where 0 == 1, so this code was wrong:
{{{
def __nonzero__(self):
return True
}}}
4. Calling .lift() on a morphism returns None. This is a bug that was
caused by cythonizing morphism.pyx:
{{{
sage: R.<x,y> = QQ[]; R.hom([x,x]).lift() is None
True
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/5756#comment:2>
Sage <http://sagemath.org/>
Sage - Open Source Mathematical Software: Building the Car Instead of
Reinventing the Wheel
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