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Unsafe (Grade A)Security-tested data-ai skill for Claude AI. Grade A. Forbid unsafe Haskell functions such as unsafePerformIO, unsafeCoerce, and other unsafe-prefixed functions. Use when writing or reviewing Haskell

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Daniel NikulshynReviewed by Daniel Nikulshyn·Updated July 2026

Overview

This skill forbids unsafe Haskell functions such as unsafePerformIO, unsafeCoerce, and other unsafe-prefixed functions. It is used when writing or reviewing Haskell code that uses any unsafe-prefixed function. The goal is to prevent the use of functions that compromise referential transparency and type safety in Haskell, which are fundamental guarantees of the language. Unsafe functions can lead to unpredictable behavior, crashes, or security vulnerabilities. The skill advises against using unsafe functions and suggests safer alternatives.

Key features

  • Detects and forbids unsafe-prefixed functions
  • Provides guidance on safer alternatives
  • Supports FFI bindings and global mutable variables with NOINLINE

Pricing

Model
Free
Category
Skills
Rating
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Use cases

Haskell Code Review

Use this skill to review Haskell code and ensure it does not use unsafe-prefixed functions.

Writing Safe Haskell Code

Use this skill to write safe Haskell code by avoiding unsafe-prefixed functions and following best practices.

Pros & Cons

Pros

  • Prevents use of functions that compromise language guarantees
  • Encourages safer coding practices
  • Helps prevent unpredictable behavior and crashes

Cons

  • May limit performance optimizations in some cases
  • Requires explicit justification for safe API design

Reviews

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Q&A

What alternatives does the skill suggest for unsafe functions?

It recommends safer equivalents like using the safe versions of library functions (e.g., indexMaybe instead of unsafeIndex), using Data.Coerce.coerce instead of unsafeCoerce, and designing APIs that avoid unsafePerformIO by encapsulating side‑effects internally.

Asked by Rina Desai · Dec 29, 2025

Can I still use unsafe functions for FFI bindings or global mutable variables?

Yes, the skill allows unsafe functions in limited cases such as FFI bindings or when combined with NOINLINE for global mutable variables, but they must be confined to internal modules and exposed only through a safe pure API with explicit justification comments.

Asked by Hiroshi Tanaka · Dec 26, 2025

What specific Haskell functions does the Unsafe skill block?

It forbids any function whose name starts with the unsafe prefix, including unsafePerformIO, unsafeDupablePerformIO, unsafeInterleaveIO, unsafeFixIO, unsafeCoerce, and library functions like unsafeIndex or unsafeRead that skip safety checks.

Asked by Cristina Moreno · Nov 21, 2025

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