Hack Lang

Hack is a programming language developed by Meta that combines fast development with static typing. It provides instantaneous type checking, typically under 200 milliseconds, making it easy to integrate into your workflow without noticeable delays.

Hack supports async functions, allowing cooperative multi-tasking. Async functions can combine I/O requests, making your code faster by reducing wait times.

XHP is a feature in Hack that provides a native XML-like representation of output (e.g., HTML). It allows UI code to be type-checked, automatically avoiding common issues like cross-site scripting (XSS) and double-escaping by escaping variables in a context-appropriate way.

Yes, HHVM and the Hack language are in active development. Meta is moving fast, making changes daily and releasing often. They encourage reporting regressions in the typechecker or runtime.

Hack supports a rich set of generic types, including type parameters, constraints, associated type constants, and even reification. This allows for more flexible and type-safe code.

Hack is built specifically for HHVM, a high-performance runtime for Hack applications. HHVM powers many large-scale sites, including Facebook.com.