Crystal
Crystal Ruby-like syntax with static typing. Use for .cr files.From its SKILL.md
npx -y skills add G1Joshi/Agent-Skills --skill crystalAssembled from the repository path, not quoted from the project. Check it against their README if it does not work.
One thing to look at
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SKILL.md
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Crystal
Crystal compiles to native code (using LLVM) but looks exactly like Ruby. v1.12 continues improving Windows support and parallelism.
When to Use
- Performance sensitive Rubyists: Porting heavy Ruby scripts to Crystal for 50x speedup.
- Microservices: Low memory footprint compared to JVM/Ruby.
- CLI Tools: Fast startup and execution.
Core Concepts
Fibers
Lightweight concurrency (like Go routines). spawn { ... }.
Macros
Generate code at compile time (like Zig/Lisp).
Union Types
String | Int32. The compiler handles the branching.
Best Practices (2025)
Do:
- Use strict types in APIs: Help the compiler with
def foo(x : Int32). - Use
shards: Dependency manager. - Use
-Dpreview_mt: To test multithreading capabilities.
Don't:
- Don't use
eval: Crystal is compiled, there is no runtime eval.
References
What ships with it
Read from the repository
Just SKILL.md. No reference files, no scripts.