#19318: Implement inverse_of_unit for IntegerModRing
-------------------------------------+-------------------------------------
Reporter: bruno | Owner:
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-6.9
Component: finite rings | Resolution:
Keywords: | Merged in:
Authors: Bruno Grenet | Reviewers:
Report Upstream: N/A | Work issues:
Branch: | Commit:
u/bruno/group_inverse_of_unit | c626f8cbf02953b94a2ca54dc0599553c0f40b47
Dependencies: | Stopgaps:
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Comment (by bruno):
Replying to [comment:3 klee]:
> Why do we need this? You can use `^-1` for the same result.
>
> {{{
> sage: R=IntegerModRing(10)
> sage: R(7)^-1
> 3
> sage: R(4)^-1
>
---------------------------------------------------------------------------
> ZeroDivisionError Traceback (most recent call
last)
> ...
> ZeroDivisionError: Inverse does not exist.
> }}}
That's right... I did not think to try to use `^-1` and I found weird not
to have an `inverse` function for these rings. And using `^-1` is actually
faster than my code! So it makes no sense to include my code within Sage.
Yet, since many rings implement a method `inverse_of_unit`, it may add
some unity (or consistency) to have one here too. So please let me know
what you think is more appropriate between:
* simply marking this ticket as "won't fix" and not providing the method
`inverse_of_unit`;
* replacing my code by something like `return self^-1` to provide a
method `inverse_of_unit`.
Note that both are fine to me, I do not have a real preference for any of
the two solutions.
--
Ticket URL: <http://trac.sagemath.org/ticket/19318#comment:4>
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