On Tue, Apr 29, 2014 at 10:57 PM, Robert Bradshaw
wrote:
> On Tue, Apr 29, 2014 at 9:07 AM, Volker Braun wrote:
>> On Tuesday, April 29, 2014 3:58:14 PM UTC+1, Simon King wrote:
>>>
>>> Yes there is! The hook is the hash function.
>>
>>
>> CPython implementation detail and subject to change... re
On Tue, Apr 29, 2014 at 9:07 AM, Volker Braun wrote:
> On Tuesday, April 29, 2014 3:58:14 PM UTC+1, Simon King wrote:
>>
>> Yes there is! The hook is the hash function.
>
>
> CPython implementation detail and subject to change... really Python makes
> no guarantee that __hash__() is called at any
On Tuesday, April 29, 2014 3:58:14 PM UTC+1, Simon King wrote:
>
> Yes there is! The hook is the hash function.
CPython implementation detail and subject to change... really Python makes
no guarantee that __hash__() is called at any particular point. Its of
course safe to normalize elements the
On 29 April 2014 16:17, Nils Bruin wrote:
> On Tuesday, April 29, 2014 7:47:39 AM UTC-7, Volker Braun wrote:
>>
>> Always putting things in canonical form will be slow (there is no hook for
>> "you are about to be put into a set") and/or not possible (fp group
>> elements).
>
>
> I disagree in thi
On Tuesday, April 29, 2014 7:47:39 AM UTC-7, Volker Braun wrote:
>
> Always putting things in canonical form will be slow (there is no hook for
> "you are about to be put into a set") and/or not possible (fp group
> elements).
>
I disagree in this particular case. Making the denominator monic is
On 29 April 2014 15:56, John Cremona wrote:
>
> I will open a ticket...
#16268 (see http://trac.sagemath.org/ticket/16268)
>
> John
>
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On Tuesday, April 29, 2014 3:35:55 PM UTC+1, John Cremona wrote:
>
> On 29 April 2014 15:16, Volker Braun >
> wrote:
> > s and t are not the same expression, so they have different hashes. We
> break
> > Python by letting them compare equal. Hence the outcome of putting them
> into
> > sets i
Hi Volker,
On 2014-04-29, Volker Braun wrote:
> Always putting things in canonical form will be slow (there is no hook for
> "you are about to be put into a set")
Yes there is! The hook is the hash function. If you need a hash (i.e.,
if you put it into a set or dict) then you need a canonical f
On 29 April 2014 15:47, Volker Braun wrote:
> On Tuesday, April 29, 2014 3:35:55 PM UTC+1, John Cremona wrote:
>>
>> On 29 April 2014 15:16, Volker Braun wrote:
>> > s and t are not the same expression, so they have different hashes. We
>> > break
>> > Python by letting them compare equal. Hence
Hi John,
On 2014-04-29, John Cremona wrote:
> That is a *very* unsatisfactory explanation for anyone actually
> wanting to use Sage to do mathematics.
+1
> That
> function could easily be amended to do the second step, which would
> make it more useful.
... and it should be used in the hash m
On 29 April 2014 15:16, Volker Braun wrote:
> s and t are not the same expression, so they have different hashes. We break
> Python by letting them compare equal. Hence the outcome of putting them into
> sets is undefined. In CPython: if the hash collides, you get one element. If
> the hash does n
s and t are not the same expression, so they have different hashes. We
break Python by letting them compare equal. Hence the outcome of putting
them into sets is undefined. In CPython: if the hash collides, you get one
element. If the hash does not collide, you get two elements.
On Tuesday, A
Hi John,
On 2014-04-29, John Cremona wrote:
> sage: s==t
> True
> sage: Set([s,t])
> {(27*u^2 + 81*u + 243)/(27*u - 81), (u^2 + 3*u + 9)/(u - 3)}
Internally, a set would first distribute the given elements in "hash
buckets". Elements in different hash buckets will not be compared by
"==". And he
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