What kind of programming language is Rhombus?

Rhombus is a general-purpose, functional, extensible programming language with good performance, extensive documentation, and practical libraries. It’s a dynamic language that offers interactivity and flexibility, but it also has the static and abstraction-enforcing constructs that are needed to scale from small scripts to large systems.

Aren’t there a lot of languages like that already?

While there are many small things we think are unique to Rhombus, including compact repetitions using ellipsis (...) and a default set of functional data stuctures with good asymptoptic complexity, the big difference is extensibility. See Rhombus Goals.

Is is fast?

Here are some benchmarks.

How do I get started?

See Getting Started.

Do I have to use DrRacket?

The DrRacket programming environment is the easiest way to get started, but see Magic Racket for VSCode or Racket mode (with its racket-hash-lang-mode major mode) for Emacs.

What is the relationship of Rhombus to Racket?

Rhombus is built on Racket, and it relies on many Racket tools, including the DrRacket programming environment and the raco command-line suite. Roughly, the languages are related in the same way as Elixir and Erlang or Kotlin and Java.

Then again, it would be fair to say that Rhombus is just Racket, because Racket is meant to be a multi-language ecosystem, and simply starting a Racket module with #lang rhombus instead of #lang racket makes it a Rhombus module. Rhombus, in turn, is meant to push Racket’s multi-language capabilities forward and enable more languages and dialects that are built on Racket and Rhombus.

Rhombus is simply Racket with a different syntax, right?

A new syntax reflects the main goal of Rhombus, but #lang rhombus also improves on #lang racket in other ways: better predefined data structures (especially lists), a new class system, pervasive pattern matching, extensible static information as a new point on the spectrum of contracts to types, hierarchical namespace organization, and more.

These general language improvements could have been implemented for a Racket dialect that’s based on S-expressions, but language–syntax codesign for Rhombus opened more possibilities and produced a whole that’s greater than the sum of the parts.

Rhombus is Racket without S-expressions, so the syntax is not homoiconic, right?

Hello, fellow Lisper! Rhombus has a bicameral syntax, where the analog to the S-expression layer is shrubbery notation. This is an important part of Rhombus’s approach to macros and metaprogramming. You might be amused by this little metacircular interpreter.

Is Rhombus useful only if I want to get into extensible languages, domain-specific languages (DSLs), and/or macros?

Using Rhombus does not necessarily mean writing macros, because Rhombus gives you everything you expect (and probably a lot more) in the base language. The fact that a rich base language is made possible by macro extensibility could be considered an implementation detail or an academic concern. If you enjoy functional, dynamic languages and are interested in a modern synthesis, Rhombus might be for you.

Are macros actually a good idea?

The design of Rhombus reflects a conviction that metaprogramming is fundamental to software construction, and that the most effective approach to metaprogramming is one that is integerated with a general-purpose language.

In particular, accomodating domain-specific languages (DSLs) within a general-purpose language avoids some common DSL pitfalls, such as siloed languages that are difficult to integrate into an application, or half-baked abstraction constructs added to a DSL that itself inevitably needs to evolve. Meanwhile, taking metaprogramming seriously benefits not only DSLs, but also metaprogramming tasks such as documentation, analysis, and tool support.

The term macro conjures a variety of meanings and connotations. The approach taken in Rhombus might be more precisely characterized as compile-time metaprogramming or an open-compiler API, but its origins are in Lisp-style macros.

Is Rhombus an academic language? A research language? A teaching language?

Rhombus is rooted in academia, but it is not a teaching language, and it is not just a research language. It is intended for production use.

Rhombus cannot yet provide the wealth of libraries available for the most widely used languages. But as an outgrowth of Racket, it has the resources and community needed to persist and evolve. Users should expect a similar level of stability, consistency, and support that Racket has offered for decades.

Do we need new programmings languages or DSLs in an age of autonomous coding agents?

Who knows?

A common early prediction around AI coding was that it would spell the end of new languages, because AI would only be able to use the most popular languages as represented in training data. That prediction has not panned out. As of May 2026, (even before Rhombus 1.0), coding agents are pretty good at writing idiomatic Rhombus code. Maybe good documentation helps.

As for DSLs, it seems possible that raising the level of discourse in programming is good for human programmers, good for autonomous programming agents, and good for conversations between them. In that case, we’ll want languages with better DSL support, and that is Rhombus’s goal.