On 2016-01-20 15:49, William Stein wrote:
All that said, without history in the way, making floordiv agree with
float floor div would be nice.
For the record, this is #15260.
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On Wed, Jan 20, 2016 at 6:38 AM, Volker Braun wrote:
> So we have never kept with the Python semantics for
> division. Not that Python has rationals out of the box anyways. Whatever
> implementation we chose, people will trip over that.
> The only thing more
> confusing than having two different b
Python 2.x also decided that integer division is C division, which we
totally violate. So we have never kept with the Python semantics for
division. Not that Python has rationals out of the box anyways. Whatever
implementation we chose, people will trip over that. The only thing more
confusing
When lurking and reading this thread, I keep being reminded of Justin
Walker's remarks that a "principle of least surprise" can be useful in
such design decisions. In this particular case, there's two things
that argue for what Jeroen suggests:
- If you have integers a and b, and write a//b th
On 2016-01-20 12:32, Volker Braun wrote:
Of course you can define as ZZ-floor division as the above operation in
QQ, but thats doesn't generalize to other rings.
True, this doesn't work in full mathematical generality. But that's not
a good reason to just throw everything away.
Many useful E
On Wednesday, January 20, 2016 at 10:22:55 AM UTC, Jeroen Demeyer wrote:
>
> In QQ, I would define a//b = floor(a/b).
> Why do you consider this not "really consistent with the division
> operation on ZZ."? Neither your previous post nor this one explains that.
>
That definition doesn't work fo
On 2016-01-20 11:17, Volker Braun wrote:
On Wednesday, January 20, 2016 at 8:28:23 AM UTC, Jeroen Demeyer wrote:
Well, you cannot have a fully consistent floor division in any case:
Either you make floor division on QQ consistent with ZZ or with QQ[x]
but you cannot have both. Person
On Wednesday, January 20, 2016 at 8:28:23 AM UTC, Jeroen Demeyer wrote:
>
> Well, you cannot have a fully consistent floor division in any case:
> Either you make floor division on QQ consistent with ZZ or with QQ[x]
> but you cannot have both. Personally, I would prefer making it
> consistent w
On 2016-01-19 22:50, Volker Braun wrote:
Presumably nobody has a problem with
sage: R. = QQ[]
sage: (3*x^2+1) // (2*x)
3/2*x
and it would be rather strange if the binary operations on the scalars
behave different in QQ vs degree-0-part(QQ[x]).
Well, you cannot have a fully consistent floor di
Presumably nobody has a problem with
sage: R. = QQ[]
sage: (3*x^2+1) // (2*x)
3/2*x
and it would be rather strange if the binary operations on the scalars
behave different in QQ vs degree-0-part(QQ[x]). Whereas it shouldn't come
as too much of a surprise that division-related operations behave
On 2016-01-19 13:31, John Cremona wrote:
This would only make sense if ZZ was the only ring of which QQ was the
field of fractions. Similarly with rational function fields, in my
opinion.
Well, you are thinking too mathematical. Of course, defining a//b = a/b
makes any field into a Euclidean
On 2016-01-19 12:49, Vincent Delecroix wrote:
1. Should we always have
a == a//b + a%b
I guess you mean
a == (a//b)*b + a%b
Buy yes, this invariant is very important and should always be satisfied.
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The behaviour for ZZ--QQ--RR decided in that other thread are taking
quotients over the sub-ring ZZ. More specifically:
if a,b are in ZZ, QQ or RR then it was decided that a % b should
implicitly satisfy:
a == (a//b) * b + a%b
and a//b in ZZ and a%b has norm smaller than b (norm as in euclidea
On 19 January 2016 at 12:37, Vincent Delecroix
<20100.delecr...@gmail.com> wrote:
> On 19/01/16 09:31, John Cremona wrote:
>>
>> On 19 January 2016 at 11:49, Vincent Delecroix
>> <20100.delecr...@gmail.com> wrote:
>>>
>>> As far as I know we do not have any specifications for //. In euclidean
>>> r
On 19/01/16 09:31, John Cremona wrote:
On 19 January 2016 at 11:49, Vincent Delecroix
<20100.delecr...@gmail.com> wrote:
As far as I know we do not have any specifications for //. In euclidean ring
it would be natural for it to be the quotient. But in other situations?
1. Should we always have
On 19 January 2016 at 11:49, Vincent Delecroix
<20100.delecr...@gmail.com> wrote:
> As far as I know we do not have any specifications for //. In euclidean ring
> it would be natural for it to be the quotient. But in other situations?
>
> 1. Should we always have
>
> a == a//b + a%b
>
> 2. Should
As far as I know we do not have any specifications for //. In euclidean
ring it would be natural for it to be the quotient. But in other situations?
1. Should we always have
a == a//b + a%b
2. Should // always be internal?
Vincent
On 19/01/16 08:28, Jeroen Demeyer wrote:
Feature or bug?
Feature or bug?
sage: QQ(7) // QQ(2)
7/2
I would expect
sage: QQ(7) // QQ(2)
3
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