Re: issquare on quadratic forms

[Sam Steingold <sds@gnu.org>]

> * Karim Belabas <Xnevz.Orynonf@zngu.h-obeqrnhk.se> [2017-12-01 19:25:07 +0100]:
>
> * Bill Allombert [2017-12-01 19:03]:
>> On Fri, Dec 01, 2017 at 12:40:14PM -0500, Sam Steingold wrote:
>>> It appears that once upon a time issquare worked on t_QFR and t_QFI, but
>>> now I get
>>>   ***   incorrect type in issquare (t_QFI).
>>> and
>>>   ***   incorrect type in issquare (t_QFR).
>>> What has happened?
>> 
>> From CHANGES-2.4:
>> 
>>    10- issquare(t_QFI or t_QFR) now is an error. Use explicitly
>>        issquare(component(x,1)) if you relied(?) on the old behaviour
>
> Note that
>
>   ? Qfb(2, 1, 3)^2
>   %1 = Qfb(2, -1, 3)
>
> whereas the old issquare code returned 0 in this case: it used to check
> whether the 'a' coefficient was a rational square (which does not make
> sense since all natural computations via '*' or '^' operators occur in
> the class group).

Indeed, I assumed that issquare(Qfb) did TRT while it was doing
something relatively uninteresting.

Thank you very much, Bill & Karim.

-- 
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