feat(language): a divisor or a power over parameters may add, so a discount factor is written where it is used

[FBumann]

Prompt: Lets do 277

Note

The following content was generated by AI.

What this changes

x / (a + b) and (1 + rate) ** years load. Arithmetic over numbers and parameters is allowed under a divisor, a base and an exponent. A variable there is still refused. Closes #277.

Why

Before this change, the degree check refused a sum anywhere under / or **, so a discount factor had to ship as a prepared column. The program already carries these trees, and the typesetter already prints them.

Method, gate output, what moved, what was not done

The change. src/math_spec/degree.py loses _adds and its two refusals. Nothing else in src/ read a divisor's shape: lowering, dimensions, boundedness and the typesetter walk already take any variable-free subtree.

Where the refusal coverage moved. The four test_degree.py refusal cases (a-sum-as-a-base, a-sum-as-an-exponent, a-divisor-that-adds, an-addition-under-a-reduction-divisor) are now cases of test_an_affine_expression_passes_everywhere. The where refusal a-divisor-that-adds in test_validation.py is now a case of test_a_where_comparing_expressions_loads, beside a new a-base-that-adds. A new typesetting test, test_a_base_that_adds_is_bracketed_and_a_divisor_that_adds_is_not, runs in every format. On the old degree.py, 9 of these fail. With the change, they pass.

Typeset, all three formats:

• LaTeX and Markdown: \left( 1 + \mathrm{cost}_{g} \right)^{2} and \frac{p_{t,g}}{\mathrm{cost}_{g} + \mathrm{p}^{\mathrm{max}}_{g}}
• Typst: (1 + ...)^(2) and frac(p_(t,g), ... + ...)

Docs.

• expressions.md replaces the single-factor paragraph with a whole model that divides by (1 + rate) ** years. The model was loaded with python -m math_spec check, and it is refused on main.
• The PyPSA stochastic example gave "a divisor is one factor" as its reason to bind 1 / (1 - alpha) as data. It now binds CVaR_alpha and writes 1 / (1 - CVaR_alpha) in CVaR-def. The gallery page is regenerated with python -m tools.gallery. The typeset row is $\theta + \frac{1}{1-\alpha} \sum_s \pi_s a_s \le CVaR$, which is PyPSA's.
• limits.md had no row for this refusal, so it does not change.

Gates.

• pixi run lint: pass.
• pixi run test: 1607 passed.
• pixi run docs-build: fails in this container because the proxy blocks https://docs.python.org/3/objects.inv. The same mkdocs build --strict passes with that one inventory removed from a temporary copy of mkdocs.yml.
• pixi run compile-tex: not run. Tectonic cannot fetch its bundle from relay.fullyjustified.net, so all 31 documents fail, changed or not. CI runs it.

Deliberately not done.

• A dimension is still not a value (Using dimensions in math expressions and masks #14, declined). (1 + rate) ** period over the dimension period is refused, and period's coordinates ship as a parameter.
• absence.md keeps "a divisor" among the positions where a missing parameter row has no value that contributes nothing. It now covers every parameter in a divisor, including the parameters of a sum.
• Not checked: whether the engines in fluxopt/lpspec compute a sum in a divisor as one value before they divide.
• Adjacent, not changed: examples/pypsa.yaml binds PyPSA's (1 - standing_loss) ** elapsed hours as data prep, which could now be derived. examples/pypsa_linearized_uc.yaml:116 says two parameters cannot be compared in a where, which the arithmetic comparison already made false.

🤖 Generated with Claude Code

https://claude.ai/code/session_01C8aNCHBtTstYhudLqHhafW

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Generated by Claude Code

[read-the-docs-community]

Documentation build overview

📚 math-spec | 🛠️ Build #34754214 | 📁 Comparing 22d7f2a against latest (086ff9a)

  🔍 Preview build  

56 files changed · + 4 added · ± 30 modified · - 22 deleted

+ Added

• first-model/index.html
• reference/api/index.html
• reference/glossary/index.html
• reference/program/index.html

± Modified

• index.html
• CHANGELOG/index.html
• contributing/index.html
• examples/index.html
• about/limits/index.html
• about/what-counts-as-language/index.html
• about/what-counts-as-public-api/index.html
• examples/pypsa/index.html
• examples/pypsa_stochastic/index.html
• howto/check/index.html
• and 20 more...

- Deleted

• reference/math_spec/advice/index.html
• reference/math_spec/boundedness/index.html
• reference/math_spec/degree/index.html
• reference/math_spec/dimensions/index.html
• reference/math_spec/errors/index.html
• reference/math_spec/exclusivity/index.html
• reference/math_spec/expansion/index.html
• reference/math_spec/lowering/index.html
• reference/math_spec/model/index.html
• reference/math_spec/operators/index.html
• and 12 more...

[FBumann]

Superseeded by #757