Furuby

Furuby is a deprecated and largely undocumented programming language that was an experimental variant of Ruby. It aimed to explore potential performance improvements by introducing static type annotations and other static analysis techniques, departing from Ruby's dynamic nature.

Specifically, Furuby sought to offer optional type annotations that programmers could use to guide the compiler. These annotations would, in theory, allow the compiler to perform optimizations that are impossible in standard Ruby due to its purely dynamic runtime. The project was intended as a research platform to explore the tradeoffs between static and dynamic typing in the context of the Ruby language and ecosystem.

While some research and experimentation were conducted, Furuby never achieved widespread adoption and development ceased. Its concepts, however, informed later efforts to improve Ruby performance and introduce gradual typing capabilities in more mainstream Ruby implementations and tools, such as Sorbet and Ruby's own type checking features. The name "Furuby" itself is a portmanteau derived from "Functional Ruby," hinting at an initial design focus towards functional programming paradigms.