[von_neumann_model] lecture improvements

[xuanguang-li]

Key changes

• Set the max-height of cells to none at the beginning
• Removed object after class Nuemann
• Adopted sphinx-proof environments

Question

• As I used the sphinx-proof, assumptions numbered as "I, II" have been changed to "1, 2". But in the definition of class Neumann, some variables are named as AI and AII. Should I change the names of these variables to A1 and A2? @mmcky

For example,

def __init__(self, A, B):

        self.A, self.B = list(map(self.convert, (A, B)))
        self.m, self.n = self.A.shape

        # Check if (A, B) satisfy the basic assumptions
        assert self.A.shape == self.B.shape, 'The input and output matrices \
              must have the same dimensions!'
        assert (self.A >= 0).all() and (self.B >= 0).all(), 'The input and \
              output matrices must have only non-negative entries!'

        # (1) Check whether Assumption 1 is satisfied:
        if (np.sum(B, 0) <= 0).any():
            self.AI = False
        else:
            self.AI = True

        # (2) Check whether Assumption 2 is satisfied:
        if (np.sum(A, 1) <= 0).any():
            self.AII = False
        else:
            self.AII = True

linked to #478

[github-actions]

🚀 Deployed on https://68a41d2b799a6a1bb51e9bd0--nostalgic-wright-5fa355.netlify.app

[Copilot]

Pull Request Overview

This PR improves the von Neumann lecture by modernizing documentation formatting and fixing minor inconsistencies. The changes primarily focus on adopting sphinx-proof environments for better mathematical presentation and updating code cell configurations.

Key changes:

• Adoption of sphinx-proof environments for assumptions, definitions, theorems, and proofs
• Removal of object inheritance from class Neumann (Python 3 style)
• Addition of CSS styling to remove cell height restrictions

[Copilot]

The TODO comment should be removed or properly formatted. If this is a genuine TODO, it should be tracked in an issue rather than left in production code.

Suggested change

	Assumptions:// TODO:change {AI} variable into A1?
	Assumptions:

[Copilot]

There is an extra closing parenthesis in the assumption title. It should be 'every good that is consumed is also produced' without the trailing parenthesis.

Suggested change

	````{prf:assumption} every good that is consumed is also produced)
	````{prf:assumption} every good that is consumed is also produced

[mmcky]

Thanks for the PR @xuanguang-li. I will take a look tomorrow.

[mmcky]

@jstac -- @xuanguang-li has asked a really nice style clarification question.

In the case where there are two or more conditions are states, should a python variable name always use numbers such as A1, A2?

What makes me pause is that in some documents Assumption admonitions can be roman numerals in style and in fact the docstring associated with this code uses roman numerals so it may be "closer to the description" keeping the roman numerals in the code.

    Both A and B have non-negative entries. Moreover, we assume that
    (1) Assumption I (every good which is consumed is also produced):
        for all j, b_{.,j} > 0, i.e. at least one entry is strictly positive
    (2) Assumption II (no free lunch):
        for all i, a_{i,.} > 0, i.e. at least one entry is strictly positive

[jstac]

so it may be "closer to the description" keeping the roman numerals in the code.

That sounds like good reasoning to me @mmcky .

[xuanguang-li]

Hi John and @mmcky,

Thanks for your feedback.

I understand your point that I should keep the variable names consistent with the docstrings. Should I still use sphinx-proof directives to write assumptions?

```{prf:assumption} every good that is consumed is also produced
:label: assumption1

$$
  b_{.,j} > \mathbf{0}\hspace{5mm}\forall j=1,2,\dots,n
$$

If I use sphinx-proof directives, Assumption admonitions will be numbered as Assumption 1 rather than in Roman numerals, as shown in the attached pictures. The reference of this assumption using {prf: ref} will also display as Assumption 1.

[mmcky]

thanks @xuanguang-li let me think this through, I take your point that we will have mixed systems in the lecture 👍

One option would be to enable roman numeral styles for sphinx-proof.

[xuanguang-li]

Thanks for your explanation. I kept the Roman numerals in the code while using the default sphinx-proof setting, as enabling Roman numerals requires editing conf.py.

Regarding the suggestion, "Only part of class Neumann(object): is showing --- show all", I tried adding a <style> tag in this file and creating a custom.css file to remove the cell height restriction, but both attempts failed. It seems I need to edit the _config.yml file instead. Are there other methods I could try, or should I leave this issue? @mmcky

[mmcky]

thanks @xuanguang-li we will always keep the css in quantecon-book-theme but thanks for giving that a go.

The collapse-20 changes the code cell to be only 20 lines wide and then adds a scroll, but I agree with you it makes it very hard to read the code.

• review style of collapse-## in the quantecon-book-theme as this has changed (perhaps downstream in sphinx_book_theme. It should expand out and collapse (as we had before).

@xuanguang-li can you make a new issue based on this issue for tracking? I would suggest using collapse-40 for now perhaps.

[xuanguang-li]

Thanks @mmcky. I have created a new issue QuantEcon/quantecon-book-theme#299 describing this problem.

[xuanguang-li]

This PR is ready for review. @mmcky @HumphreyYang

[mmcky]

@xuanguang-li could you revert this to roman numerals? I think we have kept the code the same, so these should also be roman numeral. Is that right? Thanks.

[mmcky]

thanks @xuanguang-li. Just one minor pickup.

@HumphreyYang I think this is in pretty good shape.

[HumphreyYang]

Many thanks, @xuanguang-li! Great PR!

Just two very minor comments below.

Another small comment is that I think this lecture is not yet style-sheet compliant, as some paragraphs contain more than one sentence : )

[HumphreyYang]

Here I think we want to close the definition environment after the equation.

[mmcky]

thanks @HumphreyYang.

@xuanguang-li it would be great if you could read through https://manual.quantecon.org/styleguide/writing.html and see if you make some improvements re: style guide compatibility.

[xuanguang-li]

Thanks for the comments @mmcky @HumphreyYang.

I will correct some typos and check the style again with the guidance.

[mmcky]

thanks for your work on this @xuanguang-li -- this is getting close.

[xuanguang-li]

Hi @mmcky @HumphreyYang,

I have divided the paragraphs into one sentence and used bold font to emphasize the definitions.

Do you have any suggestions or further improvements I could make?

[mmcky]

Thanks @xuanguang-li this looks good to me.

@HumphreyYang when you have time could you do a final parse of the diff.

Merge target date: 26th August 2025.

[HumphreyYang]

Many thanks @xuanguang-li and @mmcky! These changes are great improvements!

I just noticed that we might want to change ^T to ^\top according to the style sheet, and some minor typos.

I have collected them in one push above.

Once it builds I will merge if @mmcky agrees

[xuanguang-li]

Thanks for your help, @HumphreyYang. I will keep this point in mind next time.

[HumphreyYang]

Hi @xuanguang-li, I think from previous conversation, we want collapse-40 instead of collapse-20 to be there. Please let me know if I missed anything : )

[xuanguang-li]

Yes, generally it is. @HumphreyYang

But in issue #478, John says he wants to show all the code of class Nuemann.

Only part of class Neumann(object): is showing --- show all

[HumphreyYang]

Yes, generally it is. @HumphreyYang

But in issue #478, John says he wants to show all the code of class Nuemann.

Only part of class Neumann(object): is showing --- show all

Many thanks @xuanguang-li, roger that!

[mmcky]

@xuanguang-li as Humphrey suggests, let's show all for now (i.e. remove the collapse tag). I have an issue to look into the old behaviour where we could expand and show-all rather than scroll.

[xuanguang-li]

Got it, @mmcky! I'll drop the collapse-## tag when I meet it next time.

[HumphreyYang]

Many thanks @xuanguang-li and @mmcky! Merging it now!