On Friday, September 8, 2017 at 12:37:46 PM UTC-5, David Roe wrote:
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>
>
> On Fri, Sep 8, 2017 at 11:54 AM, Ben Hutz >
> wrote:
>
> Since the consensus is that P(0) etc. is too ambiguous a choice, that is
>> now #23806.
>>
>
> I don't think anyone was saying that we should change P(0), just th
On Fri, Sep 8, 2017 at 11:54 AM, Ben Hutz wrote:
> Adding coercion for scheme points is now #23805. This just address adding
> coercion through _coerce_map_from_ and does *not* allow P(0) == 0. This
> ticket does not address P(0) itself.
>
Cool; I've added some comments there.
Since the conse
Adding coercion for scheme points is now #23805. This just address adding
coercion through _coerce_map_from_ and does *not* allow P(0) == 0. This
ticket does not address P(0) itself.
Since the consensus is that P(0) etc. is too ambiguous a choice, that is
now #23806.
The bug about different
Le vendredi 8 septembre 2017 11:15:10 UTC+2, Jeroen Demeyer a écrit :
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> (I am starting to wonder if I should write a blog post explaining this,
> it's not the first time that somebody asks this).
>
Yes please !
Thank you.
Eric.
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Thanks for the additional responses.
The non-equality of the hash functions is enough to convince me that P(0)
== 0 is not worth the "convenience" of this type of coercion.
However, just to point out another inconsistency. It seems that coercion is
currently violating this hash equality in othe
On 2017-09-07 19:11, Ben Hutz wrote:
There does not appear to be an __eq__()
operator implemented for scheme points, but it does show up in tab
completion in the notebook, but can't tell me where the code is from. Is
this an artifact of starting to transition the code to python3. Or this
just br
On 7 September 2017 at 23:34, Nils Bruin wrote:
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> What is the argument that makes PP(0) == 0 bad? If PP(0) is allowed, I don't
> see how PP(0) == 0 is particularly worse.
>
> Because PP(AA(0)) and PP(BB(0)) should be different points, so it's not so
> clear which one should have precedence. PP(0
What is the argument that makes PP(0) == 0 bad? If PP(0) is allowed, I
don't see how PP(0) == 0 is particularly worse.
Because PP(AA(0)) and PP(BB(0)) should be different points, so it's not so
clear which one should have precedence. PP(0) happens to choose PP(BB(0)).
I don't think that's cano
Condensing your example; this behavior is clearly bad
sage: PP = ProjectiveSpace(QQ,1)
sage: AA = PP.affine_patch(0)
sage: BB = PP.affine_patch(1)
sage: AA is BB
True #???
I don't know of any intention to make AffineSpace globally unique, but I'd
need to look through the code to see what ha
On Thursday, September 7, 2017 at 12:10:40 PM UTC-7, Ben Hutz wrote:
>
>
> Ah. I see the difference. I don't think it is unreasonable for P(0) == 0
> to work in dimension 1 as there is a canonical answer. So I would have to
> say yes, I'm working on having that coercion work.
>
I think it is unr
On Thursday, September 7, 2017 at 1:16:12 PM UTC-5, David Roe wrote:
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>
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> On Thu, Sep 7, 2017 at 2:00 PM, Ben Hutz >
> wrote:
>
> Once you construct P(0), both a and P(0) are in the same parent, so there
> are no coercions involved in the test a==P(0). In your branch, what does
> sage: a.p
On Thu, Sep 7, 2017 at 2:00 PM, Ben Hutz wrote:
> Yes, but *after* implementing the coercion for the homsets I'm getting the
> behavior above. The 'a==0' doesn't go through the coecion framework, but
> the a==P(0) does. So one returns true and the other false. I'm trying to
> figure out why == is
Yes, but *after* implementing the coercion for the homsets I'm getting the
behavior above. The 'a==0' doesn't go through the coecion framework, but
the a==P(0) does. So one returns true and the other false. I'm trying to
figure out why == is not utilizing the coercion/richcmp in that case.
You'
On Thu, Sep 7, 2017 at 1:46 PM, Ben Hutz wrote:
> Yes, I'm working on the coercion now.
>
> However, isn't a==0 checking coercion from the parent of a to the parent
> of 0. In other words, the homset of rational points on P and QQ.
>
Yes, I got confused by the notation, since normally in Sage P(
Yes, I'm working on the coercion now.
However, isn't a==0 checking coercion from the parent of a to the parent of
0. In other words, the homset of rational points on P and QQ.
In dimension 1, there is a canonical coercion, but not in higher dimensions.
On Thursday, September 7, 2017 at 12:17:57
The reason that a==0 returns false is that there is no coercion map from QQ
to P:
sage: P.has_coerce_map_from(QQ)
False
I'm not convinced that there should be a coercion, it's pretty rare that a
scheme has a natural map from its base ring.
However, it seems like there's also a problem hiding here
I'm working on implementing coercion for scheme points and had a question
about how comparison is done. As an explicit example consider the following
point
P.= ProjectiveSpace (QQ ,1)
a=P(0)
in particular, the integer 0 is coerced into the projective point (0:1).
For comparisons it appears tha
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