.cr File — Crystal Source Code

Crystal is a statically-typed, compiled programming language with syntax heavily inspired by Ruby, designed to provide Ruby's elegance and productivity with C-like performance. Created in 2014, Crystal compiles to native code via LLVM, producing fast executables without the runtime overhead of interpreted languages. CR files contain source code featuring Ruby-inspired syntax with blocks, method definitions, classes, modules, and mixins, combined with static type checking through global type inference that rarely requires explicit type annotations. Crystal supports union types, generics, macros for compile-time code generation, fibers for concurrent programming, channels for communication between fibers, and C bindings for interoperability with existing libraries. The language aims to let developers write code that looks and feels like Ruby but runs at compiled speeds. Crystal has gained adoption for web services (Kemal, Lucky, Amber frameworks), CLI tools, and system utilities where both developer productivity and runtime performance are important. The standard library provides comprehensive support for HTTP, JSON, YAML, databases, and cryptography. Shards is Crystal's package manager.