--- name: logic-diff description: "Compare two code versions for semantic equivalence via semi-formal tracing of both versions side-by-side." risk: safe source: https://github.com/hyhmrright/logic-lens/tree/main/skills/logic-diff source_repo: hyhmrright/logic-lens source_type: community date_added: 2026-07-01 license: MIT license_source: https://github.com/hyhmrright/logic-lens/blob/main/LICENSE --- # Logic-Lens — Semantic Diff ## When to Use Use this skill when you need compare two code versions for semantic equivalence via semi-formal tracing of both versions side-by-side. Trigger when the user shares a refactor, rewrite, migration, or A/B implementation and wants to confirm behavior is unchanged — "did I break anything", "is this equivalent", "are... ## Supporting prerequisites Both tracked files are bundled, but the referenced sibling `_shared/` library is not. Its L-codes, language rules and report template cannot be claimed as loaded here. Use the inline five-field finding structure and explicitly scoped traced scenarios unless a reviewed matching upstream installation supplies those shared files. ## Setup Use lazy loading per `../_shared/common.md` §13: 1. Read `../_shared/common.md` only for language, Iron Law, Verdict header, scope routing, Remedy discipline, config fields, and loading budget. 2. Read only the relevant step in `logic-diff-guide.md` as you reach it. 3. Load `../_shared/logic-risks.md`, `../_shared/semiformal-guide.md`, `../_shared/semiformal-checklist.md`, and `../_shared/report-template.md` on demand when the current step needs them. ## Process **Step 0. Language + scope routing.** Detect language per `common.md` §1. Confirm two versions are provided. If only one version, switch to logic-review. **Step 1. Identify the shared specification** (guide Step 1) — what inputs should both versions handle; what outputs/side effects are expected. If the user states the refactor intentionally changed behavior in a specific area (e.g., "I changed the error path to raise instead of returning None"), record that as a **declared spec change** and treat divergences within that area as expected. Flag only divergences outside the declared change as findings. **Step 2. Build independent premises for each version** (guide Step 2) — apply the Premises Construction Checklist to Version A and Version B separately. **Step 3. Trace both versions for the common case** (guide Step 3) — parallel trace, same input, note the first divergence if any. **Step 4. Trace boundary cases** (guide Step 4) — empty/null/zero, max/min, error inputs, first/last of collections. Start with at most three highest-risk boundary scenarios unless the user asks for exhaustive equivalence or the shared specification requires more. **Step 5. Identify and classify semantic divergences** (guide Step 5) — each divergence is a finding with Premises → Trace → Divergence → Trigger → Remedy and an L-code. **Step 6. Equivalence verdict** (guide Step 6) — one of: `✅ Semantically Equivalent`, `⚠️ Conditionally Equivalent` (state the condition precisely), `❌ Semantically Divergent`. **Step 7. Output** (guide Step 7) — Report Template with the Verdict header per `common.md` §5; localize headers if the user wrote in Chinese. **Format is mandatory even for trivially short snippets: every divergence finding MUST use the five labeled fields (Premises / Trace / Divergence / Trigger / Remedy); never substitute with a plain paragraph or table.** **Mode line in report:** `Semantic Diff` (Chinese: `语义对比`). ## Limitations - Use this skill only when the task clearly matches its upstream source and local project context. - Verify commands, generated code, dependencies, credentials, and external service behavior before applying changes. - Do not treat examples as a substitute for environment-specific tests, security review, or user approval for destructive or costly actions. --- Source attribution: hyhmrright/logic-lens contributors, via Agentic Awesome Skills Original project: https://github.com/hyhmrright/logic-lens License: MIT + CC-BY-4.0 License information: https://creativecommons.org/licenses/by/4.0/ Original upstream instructions; downloaded from Mega AI Hub. ## Upstream license notice MIT License Copyright (c) 2026 Logic-Lens Contributors Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. # Mega AI Hub resource metadata Creator / publisher: hyhmrright/logic-lens contributors, via Agentic Awesome Skills Original project: https://github.com/hyhmrright/logic-lens Attribution basis: Recorded upstream repository Fields of work: Development & Engineering Roles: Software Developer Specialties: Specialty not specified Tools: Tool not specified Country applicability: Country not specified Classification basis: Dave AI task classification from package title, description, and declared metadata Instruction SHA-256: e3233e754682d7b7e866ce4632cd05c906f3edc0fa6e5f04fdb8306437599891 Metadata reviewed: 2026-10-27 This metadata supersedes earlier Mega AI Hub catalog attribution. Original instruction and supporting files are preserved.