fix: propagate NaN in Matrix::inf_norm (#85)

[acgetchell]

Matrix::inf_norm() silently returned 0.0 for matrices containing NaN entries because NaN > max_row_sum always evaluates to false, so NaN rows were skipped entirely. This contradicts the expected mathematical behavior that any NaN entry contaminates the norm.

• Detect NaN row sums explicitly and short-circuit to f64::NAN (marked cold_path()). Preferred f64::maximum is still unstable behind float_minimum_maximum as of Rust 1.95, so the explicit check is used instead.
• Document NaN/Inf behavior with a new "Non-finite handling" section and a NaN doctest.
• Add regression tests across D=2..=5 via a macro: all-NaN → NaN, single-NaN → NaN, +∞ entry → +∞.

Tests: just ci — 98 lib, 26 doc, 259 exact-feature, 101 Python, all examples, all linters/validators.

Closes #85

Summary by CodeRabbit

• Bug Fixes

  • Improved handling of NaN values in matrix calculations to ensure proper propagation instead of being ignored in comparisons.

• Documentation

  • Enhanced documentation specifying NaN and infinity behavior in matrix operations.

• Tests

  • Added regression tests verifying correct handling of edge cases with NaN and infinity values.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 4c4d22be-c341-474e-a1e2-be67f7c6cc0c

📥 Commits

Reviewing files that changed from the base of the PR and between 56973bc and 16ffa45.

📒 Files selected for processing (1)

• src/matrix.rs

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📝 Walkthrough

Walkthrough

The Matrix::<D>::inf_norm() method was updated to explicitly detect NaN row sums and return f64::NAN immediately using cold_path(), preventing silent incorrect results. Documentation expanded to specify NaN/∞ propagation semantics. Regression tests added covering all-NaN matrices, single NaN entries, and infinity propagation across dimensions 2–5.

Changes

Cohort / File(s)	Summary
NaN detection and documentation src/matrix.rs	Enhanced inf_norm() with explicit NaN row sum detection and immediate f64::NAN return via cold_path(). Updated method documentation to specify NaN/∞ propagation semantics. Added regression tests for all-NaN matrices, single NaN entries, and infinity entries across dimensions D=2–5.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 A matrix once lost in the NaN,
Now returns what it should, not a plan!
No more hiding, no more lies—
The infinity now truthfully flies! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix: propagate NaN in Matrix::inf_norm (#85)' accurately and concisely describes the main change: fixing NaN propagation in the inf_norm method, and references the issue number.
Linked Issues check	✅ Passed	The implementation correctly addresses issue #85 by explicitly detecting NaN row sums and returning f64::NAN immediately, providing the correct behavior specified in the issue requirements.
Out of Scope Changes check	✅ Passed	All changes are scoped to fixing NaN propagation in Matrix::inf_norm() with documentation updates and regression tests, directly addressing issue #85 with no unrelated modifications.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/85-inf-norm-nan-propagation

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.65%. Comparing base (56973bc) to head (16ffa45).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #92      +/-   ##
==========================================
+ Coverage   88.58%   88.65%   +0.07%     
==========================================
  Files           5        5              
  Lines         482      485       +3     
==========================================
+ Hits          427      430       +3     
  Misses         55       55              

Flag	Coverage Δ
unittests	88.65% <100.00%> (+0.07%)	⬆️

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[acgetchell]

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