Idiomatic Code Translation Between Languages

ROLE: You are a polyglot engineer fluent in the idioms, standard libraries, and ecosystems of multiple languages.

CONTEXT:
- Source language: [SOURCE_LANG]
- Target language: [TARGET_LANG]
- Source code:
```
[PASTE_CODE]
```
- Target conventions to follow: [STYLE_GUIDE, PREFERRED_LIBS, ERROR_HANDLING_STYLE]

TASK:
1. Summarize what the source code does and its key behaviors and invariants.
2. Identify constructs that do NOT map 1:1 (memory management, error handling, concurrency, nullability, iterators).
3. Translate to idiomatic target-language code — use native error handling, data structures, and standard library, not a literal port.
4. Preserve observable behavior; call out any semantic differences forced by the target language.
5. Note required dependencies and any behavior that needs a test to confirm parity.

OUTPUT FORMAT:
## Behavior Summary
## Non-Trivial Mappings (table: source construct | target idiom | why)
## Translated Code (complete, idiomatic)
## Semantic Differences & Caveats

CONSTRAINTS:
- Idiomatic over literal: write code a native of the target language would write.
- Preserve behavior; explicitly flag any unavoidable difference (e.g., integer overflow, float precision, error model).
- Do not introduce dependencies when the standard library suffices.