verse-lab

verse-lab / velvet

Public

An auto-active verifier embedded into Lean

dafny lean
22
0
100% credibility
Found Feb 17, 2026 at 21 stars -- GitGems finds repos before they trend. Get early access to the next one.
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AI Analysis
Lean
AI Summary

Velvet is a verifier tool embedded in the Lean proof assistant that checks imperative programs for correctness using automated math solvers and interactive proofs.

How It Works

1
🔍 Discover Velvet

You hear about Velvet, a helpful tool that checks if your step-by-step instructions always produce the right results, like a super-smart proofreader for recipes.

2
📚 Get the Lean toolkit

You pick up the free Lean program, a friendly math playground where you can write simple algorithms and prove they work every time.

3
🔗 Add Velvet to your project

You connect Velvet to your Lean project with one easy line, so it can start helping with the checks.

4
🔨 Prepare everything

You hit the build button to set up Velvet and its helpers, and it grabs what it needs automatically.

5
✍️ Write and specify your instructions

You describe your algorithm and add promises about what it should do before and after, feeling confident as Velvet understands your goals.

6
✅ Prove it works

Velvet automatically checks your promises using math magic, or you guide it interactively when needed, watching proofs light up green.

7
🧪 Run quick tests

You test your instructions with random examples to double-check they behave as promised in real scenarios.

🎉 Fully verified success

Your instructions are now mathematically proven correct, including that they always finish, ready for use without worries!

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AI-Generated Review

What is velvet?

Velvet is an auto-active verifier embedded into Lean for imperative programs, mimicking Dafny with specs like requires, ensures, and invariants. It auto-proves via SMT solvers cvc5 and z3, switches to interactive Lean tactics or property-based testing when needed, and verifies partial/total correctness plus non-determinism. Just add it to your lakefile.lean to compile, execute, and formally check code in one Lean environment, tapping mathlib for specs.

Why is it gaining traction?

It stands out by blending automated SMT proofs with Lean's interactive mode and testing, unlike siloed tools—SMT fails, you grind on seamlessly. Developers hook on the unified workflow for multi-modal verification, handling real-world non-determinism and termination without tool-switching. Early buzz from Lean formalists praising mathlib integration over pure Dafny limits.

Who should use this?

Lean theorem provers tackling imperative algos like sorting, matrix math, or substring search with formal guarantees. Suited for researchers mixing automated and manual proofs, or safety-focused devs verifying recursion and loops beyond basic types.

Verdict

At 19 stars and 1.0% credibility score, Velvet feels alpha—sparse docs, limited examples, no broad testing—but delivers real value for niche Lean verification. Worth a spin for formal methods tinkerers; hold off for teams needing mature stability.

(178 words)

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