Analyze Function

Perform a thorough line-by-line analysis of a function, explaining not just what the code does but why it's written this way.

When to Use

• Understanding unfamiliar or complex code
• Onboarding to a new codebase
• Pre-refactor deep understanding
• Performance investigation
• Code archaeology (understanding legacy code intent)
• Learning from well-written code

Process

1. Parse Request

Extract:

• File path containing the function
• Function/method name to analyze

Formats to recognize:

• {file}:{function_name}
• {function_name} in {file}
• Just {function_name} (search for it)

2. Locate the Function

1. Read the file
2. Find the function definition
3. Identify the full scope (including nested functions, closures)
4. Note the line numbers

3. Gather Context

Before line-by-line analysis, understand:

• What module/class is this part of?
• What calls this function? (if easily determinable)
• What does this function call?
• Any relevant types, interfaces, or data structures

4. Analyze Each Line

Open ANALYSIS-GUIDE.md for the detailed framework.

For every line, consider:

• What: Technical explanation of what this line does
• Why: Rationale for this approach (not just restating the what)
• Note: Performance implications, edge cases, or gotchas (when relevant)

Do not skip "boring" lines. Every line exists for a reason.

5. Identify Critical Details

After line-by-line, explicitly list things that might be missed on casual reading:

• Implicit assumptions the code makes
• Non-obvious behavior or side effects
• Hidden dependencies
• Subtle edge cases
• Error conditions that aren't obvious

6. Note Design Patterns

If the function uses notable patterns or techniques, name them:

• Design patterns (Factory, Observer, etc.)
• Language idioms
• Performance optimization techniques
• Error handling patterns

7. Suggest Improvements (If Any)

Only if genuine concerns exist:

• Potential bugs or edge cases not handled
• Performance issues
• Readability improvements
• Missing error handling

Do not invent issues. If the code is solid, say so.

Output Format

## Function Analysis: {function_name}

**File**: `{path/to/file.ext}`
**Lines**: {start}-{end}
**Language**: {language}

### Context & Purpose

{2-3 sentences: What this function does, where it fits in the system, why it exists}

### Line-by-Line Analysis

**Line {N}**: `{code}`
- **What**: {technical explanation}
- **Why**: {rationale for this approach}
- **Note**: {performance implication, edge case, or gotcha}

**Line {N+1}**: `{code}`
- **What**: {explanation}
- **Why**: {rationale}

{Continue for all lines...}

### Critical Details

Things that might be missed on casual reading:

- {Non-obvious behavior or assumption}
- {Hidden dependency or side effect}
- {Subtle edge case}

### Design Patterns

- **{Pattern name}**: {How it's applied here}

### Potential Improvements

{If any genuine issues exist:}
- {Concern}: {explanation}

{Or if code is solid:}
No significant issues identified. The implementation is {brief positive assessment}.

Guidelines

• Be thorough: Every line matters. Don't summarize or skip.
• Explain why, not just what: "Initializes counter to 0" is useless. "Starts at 0 because indexes are zero-based and we're tracking position" is useful.
• Be honest about uncertainty: If you're not sure why something is done a certain way, say so.
• Connect to context: How does this line relate to the function's purpose?
• Note the non-obvious: What would trip up someone reading this quickly?