Implement function-like macros

[Copilot]

The preprocessor supported only object-like macros (#define FOO value). This adds function-like macros with parameters.

Changes

Core implementation:

• Added FunctionLikeMacro class to represent macros with parameters and body
• Modified process_define to detect function-like macros (immediate ( after name) and parse parameter lists
• Enhanced TokenExpander to:
  • Detect macro invocations (name followed by ()
  • Extract arguments with parenthesis depth tracking
  • Expand arguments recursively before substitution
  • Maintain recursion guards per-expander instance

Behavior:

• Arguments are fully expanded before substitution into macro body (enables nested calls)
• Macro name without () is not expanded (treated as identifier)
• Malformed definitions fall back to object-like behavior

Example

#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define SQUARE(x) ((x) * (x))

MAX(1, 2)           // expands to: ((1) > (2) ? (1) : (2))
SQUARE(SQUARE(3))   // expands to: ((((3) * (3))) * (3))
MAX                 // not expanded (no parentheses)

Documentation

Updated README to document function-like macro support, including limitations (no stringification # or token pasting ## operators).

Original prompt

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This section details on the original issue you should resolve

<issue_title>Function-like macros</issue_title>
<issue_description>- [ ] Design system for expanding function-like macros

• Update readme to align with current capabilities </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Function-like macros #88

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.90%. Comparing base (1ef46e6) to head (98e6df8).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #89      +/-   ##
==========================================
+ Coverage   97.53%   97.90%   +0.37%     
==========================================
  Files           7        7              
  Lines         648      763     +115     
  Branches      127      160      +33     
==========================================
+ Hits          632      747     +115     
  Misses         10       10              
  Partials        6        6              

Files with missing lines	Coverage Δ
simplecpreprocessor/core.py	96.40% <100.00%> (+0.51%)	⬆️
simplecpreprocessor/tokens.py	97.80% <100.00%> (+1.47%)	⬆️

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