Fix \texttt{} in display math contexts

[lefticus]

Problem

Remaining \texttt{} macros in markdown output, primarily in math contexts. Analysis shows:

• n4950: 23 instances
• trunk: 39 instances
• Total: 62 instances

Root Cause

\tcode{} macros preserved in math mode by Pandoc, appearing as \texttt{} in output.

Solution

Extended cpp-math.lua to handle display math contexts:

1. Display Math Handler: Added elseif elem.mathtype == "DisplayMath" branch

   • Converts \tcode{}/\texttt{} to backticks before Unicode conversion
   • Applies preprocessing (strips \placeholder{}, \ensuremath{}, text macros)
   • Uses all-or-nothing approach: fully convert to Unicode or revert to preprocessed LaTeX

2. Test Coverage: Added 4 new tests in test_math.py:

   • test_texttt_in_display_math() - Basic display math blocks
   • test_tcode_in_display_math() - XOR operator handling
   • test_multiple_texttt_in_display_math() - Multiple macros
   • test_texttt_in_complex_display_math() - Multi-line \begin{align*}

Results

• n4950: 23 → 14 instances (39% reduction, 9 fixed)
• Test suite: 483 → 487 tests, all passing

Remaining Edge Cases (14 instances)

• Nested \texttt{\textit{}} (containers.md)
• Escaped special chars \texttt{\} (lex.md)
• Complex inline math (ranges.md)
• Escaped underscores (utilities.md)

These harder edge cases require more sophisticated handling and can be addressed in future work.

Files Changed

• src/cpp_std_converter/filters/cpp-math.lua - Display math handling
• tests/test_filters/test_math.py - 4 new tests

[lefticus]

Attempted Solution (Failed)

Tried extending cpp-math.lua to handle display math contexts by adding a DisplayMath handler that:

1. Converted \tcode{}/\texttt{} to backticks
2. Stripped text macros and \ensuremath{}
3. Skipped Unicode conversion to avoid partial conversions

Problem: This approach processed ALL display math elements, not just ones containing \texttt{}. This caused unwanted side effects like:

• Converting existing Unicode math back to LaTeX (π → \pi, ≤ → \le)
• Reformatting complex math expressions
• Affecting math that was already correctly formatted

Lessons Learned:

• Need to check if \tcode{}/\texttt{} exists in the math text BEFORE processing
• Should only apply transformations to affected elements
• Display math filter should be more selective

Next Steps:

• Guard the DisplayMath handler with a check: only process if text contains \tcode{ or \texttt{
• May need to handle this earlier in the pipeline (simplified_macros.tex) instead
• Consider if display math \texttt{} is actually a problem worth fixing (only 5% of total instances)

Changes rolled back. Issue remains open for future solution.