m04-zero-cost skillA
m04-zero-cost is agent-read markdown (skill) from moeru-ai/auv: CRITICAL: Use for generics, traits, zero-cost abstraction. Triggers: E0277, E0308, E0599, generic, trait, impl, dyn, where, monomorphization, static dispatch, dynamic dispatch, impl Trait, trait bound not satisfied, 泛型, 特征, 零成本抽象, 单态化.
Indexed from public GitHub and served as immutable, content-addressed versions. Install it pinned to an exact SHA-256 with the mdr CLI, and every file is verified against the hash recorded here before it reaches your agent. The deterministic audit below grades the latest version, and the same file always earns the same grade.
What the file says
# Zero-Cost Abstraction > **Layer 1: Language Mechanics** ## Core Question **Do we need compile-time or runtime polymorphism?** Before choosing between generics and trait objects: - Is the type known at compile time? - Is a heterogeneous collection needed? - What's the performance priority? --- ## Error → Design Question | Error | Don't Just Say | Ask Instead | |-------|----------------|-------------| | E0277 | "Add trait bound" | Is this abstraction at the right level? | | E0308 | "Fix the type" | Should types be unified or distinct? | | E0599 | "Import the trait" | Is the trait the right abstraction? | | E0038 | "Make object-safe" | Do we really need dynamic dispatch? | --- ## Thinking Prompt Before adding trait bounds: 1. **What abstraction is needed?** - Same behavior, different types → trait - Different behavior, same type → enum - No abstraction needed → concrete type 2. **When is type known?** - Compile time → generics (static dispatch) - Runtime → trait objects (dynamic dispatch) 3. **What's the trade-off priority?** - Performance → generics - Compile time → trait objects - Flexibility → depends --- ## Trace Up ↑ …
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How to install
mdr add moeru-ai/auv/m04-zero-cost@git:20260725.8a8e541mdr add moeru-ai/auv/m04-zero-cost@sha256:3a2eed8faf0a0087Pin to a label to follow the author's releases, or to a sha256 to freeze the exact bytes forever. Either way the resolved hash is written to mdr.lock, and mdr install reproduces it on any machine.
[](https://markdownregistry.com/a/art_l3axua4zyf6sahee)
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Audit of the latest version
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- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
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- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
moeru-ai/auv · 50 stars · license Apache-2.0 · pushed 2026-09-23 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_l3axua4zyf6sahee GET https://markdownregistry.com/api/v1/resolve?ref=moeru-ai/auv/m04-zero-cost GET https://markdownregistry.com/api/v1/blob/3a2eed8faf0a0087aa5c823d66341123cc6f43ef36d1767c3fdbcc86cf8b4b54
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