patch for the printing of quantum.spin

[krastano...@gmail.com]

Following from here http://groups.google.com/group/sympy/msg/accc99bb1030e6b2
Concerning issue http://code.google.com/p/sympy/issues/detail?id=2251

As the printing of spin states in physics.quantum is a bit ambiguous I have tried to change it. I have override the _print_content* methods to add a prefix.
As this is the first time I work with the printing system I would be grateful if someone checks the consistency of the approach. Most importantly - I do not know if my approach is what you have in mind for general spin states.

If it is consistent I will check the unit tests (it's not done for the moment)

Regards
Stefan

[krastano...@gmail.com]

By the way there is something that is not immediately obvious to me (concerning InnerProduct and a bug in my patch):

This is ok:
JzKet('1/2','1/2')   ==>  ❘z:1/2,-1/2⟩
JxKet('1/2','1/2')   ==>  ❘x:1/2,-1/2⟩
TimeDepKet('psi', 't')  ==> ❘ψ;t⟩

This is probably ok:
TimeDepKet('psi', 't').dual * TimeDepKet('psi', 't')  ==> ⟨ψ❘ψ;t⟩  # Only one t

This is NOT ok:
JxKet('1/2','1/2').dual*JzKet('1/2','1/2')  ==> ⟨1/2,-1/2❘z:1/2,-1/2⟩ # The x is lost, the output is not clear.

What should be done?

Regards
Stefan

[Julien Rioux]

> *This is NOT ok:*

> JxKet('1/2','1/2').dual*JzKet('1/2','1/2')  ==> ⟨1/2,-1/2❘z:1/2,-1/2⟩ # The
> x is lost, the output is not clear.
>
> What should be done?

.dual returns the J?Bra classes. You didn't define
_direction_string_label for these classes.

[krastano...@gmail.com]

That is not the problem _but_ It is true that I should define _direction_string_label for J?Bra for another reason.

With the patch (and no _direction_string_label for the J?Bras) I have
JxKet('1/2','1/2').dual  ==> ⟨z:1/2,-1/2❘
which is ok.

The problem is that innerproduct uses print_label and not print_content for the bra which is the way it should be, at least for TimeDepKet.

Adding _direction_string_label to J?Bra is needed because someone may define a Bra and get
JxBra('1/2','-1/2')  ==> ⟨None:1/2,-1/2❘. Otherwise it is not needed for the use of Ket.dual as the field is already defined.

Stefan

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[Julien Rioux]

On Apr 1, 12:21 pm, "krastanov.ste...@gmail.com"

<krastanov.ste...@gmail.com> wrote:
> The problem is that innerproduct uses print_label and not print_content for
> the bra which is the way it should be, at least for TimeDepKet.
>

I see. Well I don't agree that ⟨ψ❘ψ;t⟩ is how it should be. I think it
should be ⟨ψ;t❘ψ;t⟩.

[Brian Granger]

+1

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Brian E. Granger
Cal Poly State University, San Luis Obispo
bgra...@calpoly.edu and elli...@gmail.com

[krastano...@gmail.com]

If there is a consensus on this I will be happy to change it.

Otherwise is the patch ok? If it is to whom should I send it?
Here is the second part that adds _distance_string_label to the bras

[Vinzent Steinberg]

On 1 Apr., 18:31, "krastanov.ste...@gmail.com"

<krastanov.ste...@gmail.com> wrote:
> If there is a consensus on this I will be happy to change it.
>
> Otherwise is the patch ok? If it is to whom should I send it?
> Here is the second part that adds _distance_string_label to the bras

The preferable way is to create a pull request on github. Email
patches are fine too with me, but I don't know about the quantum guys.

Vinzent

[krastano...@gmail.com]

Thanks. Brian also explained it in a private message.

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[krastano...@gmail.com]

Hi

I have a question about the behavior of _print_contents. As it stands there is no difference between _print_contents and _print main method. _print just calls _print_contents. That way _print_content must take care for the brackets. I believe this is counterintuitive. And it makes it difficult to fix the printing of InnerProduct in a clear way.

I propose that the bracket printing is done in the main method _print and that _print_contents is left printing only the content of those brackets. That way the printing of InnerProduct will be much more easy to understand.

As it stands there is no easy way to print bra*ket. If I use _print_label it will only print the quantum numbers and not the time (for TimeDepBra) or the direction string (for J?Bra). If I use _print_contents the left bracket and the vertical line are printed twice.

Stefan

[krastano...@gmail.com]

My proposition may be detrimental for _sympyrepr in qexpr.py. Is it?
Should _print_contents print the brackets or not?

[krastano...@gmail.com]

Ok, there is a pull request.