Crystal

What Crystal is not

• A Ruby implementation

What Crystal is

Language goals:

• Have a syntax similar to Ruby (but compatibility with it is not a goal)
• Statically type-checked but without having to specify the type of variables or method arguments.
• Be able to call C code by writing bindings to it in Crystal.
• Have compile-time evaluation and generation of code, to avoid boilerplate code.
• Compile to efficient native code.

For Rubyists

• ~= Ruby
  • • Compiled (= very fast)
  • • Types
  • • Comprehensive standard library
  • • Metaprogramming
  • • A different kind of metaprogramming

Types

Inference

Union Types

Method overload

Generics

Macros

~ methods, but:

• Compile time
• Generates the code that will be compiled

Concurrency

• Channels
• Fibers/spawn
• Reminder that concurrency != parallelism

Ecosystem

• Kemal
• Lucky
• crystal-{mysql,pg,redis}
• Sidekiq.cr
• SDL

Documentation

• https://crystal-lang.org/
• https://crystal-lang.org/docs
• https://crystal-lang.org/api
• https://github.com/veelenga/awesome-crystal