| name | general-decomposition |
| description | Use when reviewing any codebase for file bloat, excessive nesting, DRY violations, hand-rolled algorithms, and decomposition opportunities. Universal structural truths independent of language or framework. |
General Decomposition Domain Knowledge
Universal structural concerns applicable to any codebase. These are truths about code organisation, not about any specific language or framework.
Responsibility Groups
A responsibility group is a cohesive unit of functionality that could live in its own file. Recognise these types:
- A class or struct definition with its own API surface
- A cluster of free functions that operate on the same data type or concept
- A self-contained algorithm (sort, search, transform) embedded in a larger file
- A block of type definitions (enums, type aliases, constants) serving a specific subsystem
Language- or framework-specific group types (e.g. UE UCLASS, USTRUCT, processor logic) are defined in companion domain skills.
DRY Violations
Flag logic blocks that appear more than once in the same file with only minor variation:
- Duplicated blocks — identical or near-identical code in two or more places. Recommend extraction to a named helper. Quote the repeated logic and name the proposed function.
- Semantic inversions — method pairs whose bodies are structurally identical but differ only in a scalar, sign, direction, or enum value (e.g.,
GoBack() / GoForward() differing only in +1 / -1). Recommend merging into a single parameterised method.
- Do NOT use
const_cast as a de-duping approach. APIs must still respect const-correctness.
Hand-Rolled Algorithms
Flag manual loops that replicate well-known library functions. Name the specific replacement and cite the header or module.
Comments as Decomposition Signals
- A conditional block with an explanatory comment is a helper function the implementer overlooked. If code needs a comment to explain what a branch does, that branch should be a named function.
- Comments in headers can be important. Design-intent comments, API contracts, and summary docs are legitimate.
- Comments in implementation files explaining what code does (not why) are a smell. The abstraction level is wrong.
- "Section header" comments (e.g.,
// --- Handle tile remapping ---) are almost always responsibility group boundaries. The implementer identified the seam but didn't act on it.
Nesting Depth
- Two levels is normal: function scope + one conditional or loop.
- Three levels is occasional: function scope + outer loop + inner loop.
- Four or more levels is a RED FLAG. Report with specific remediation.
Common causes
- Pointer-checking chains — cascading
if (Ptr) { if (Ptr->Inner) { ... }}. Leaky abstraction boundaries. Fix: accessor or helper that encapsulates the traversal.
- Missing helper functions — deeply nested logic that could be named and extracted.
- Inlined state machine transitions — switch/case with nested conditionals per case. Extract each case body into a named handler.
When nesting resists reduction
If you cannot decompose a deeply nested block — if every helper produces an incoherent signature requiring 6+ parameters — that signals the design is missing an axis of abstraction. A struct, a policy object, a visitor, or a different data representation would eliminate the nesting at the source. Report this as BLOCKING with your analysis of what abstraction is missing.
Decomposition is a pressure cooker for auditing the design. If it resists decomposition, the problem is upstream.
Decomposition Execution Rules
When proposing or executing a decomposition:
- Purely mechanical. Extract, move, adjust includes. Do not redesign, optimise, or "improve" logic during extraction.
- Follow existing patterns. If the codebase already has a convention for file splitting (e.g., one class per file, helpers in a
*Utils.h), follow it.
- No renaming during extraction. Rename in a separate, dedicated pass — not interleaved with structural moves.
- No logic changes. The extracted code must behave identically. If you spot a bug, flag it separately.
- Preserve include hygiene. After extraction, each file must include only what it directly uses.
- Preserve test structure. If tests reference moved symbols, update the includes — do not reorganise test files as part of a decomposition.
