Rhombus is a new language (version 1.0 as of June 2026) that is built on Racket. It offers the same kind of language extensibility as Racket, but using conventional (infix) notation, multiple and user-definable binding spaces for context-specific extensible sublanguages, and a framework for type-like static information. This talk will provide an overview of Rhombus, and we’ll look at the Rhombus foreign-function interface to C as an example language extension that has its own syntax, adds its own binding space, and relies on static information for checking and performance.

Matthew Flatt is a professor in the School of Computing at the University of Utah, where he works on extensible programming languages, runtime systems, and applications of functional programming. He is one of the developers of the Racket programming language. He received his PhD from Rice University in 1999.