Oluś: a Pure Continuation-Passing-Style Language

fact n return:
    if (is_zero n) (:return 1) (:)
    return (mul n (fact (sub n 1)))

I've always been facinated by programming languages and proof systems (they are closely related). In particular I'm fascinated by expressive minimal languages like Lisp, Forth and Metamath. These repesent some stable local optima in the design space of languages. They are simple, expressive and powerful. They are also very different from each other. I've been exploring for a long time what the next stable optimum may look like, and I gravitated towards a language that takes continuation-passing-style to the extreme. As far as I know, such a language has not been implemented before.

Over many years I've build several compilers (e.g. 1 2 3 4) for variants of this language, some of which had unique properties. Pure CPS does not require a stack and one compiler produced x86 assembly that did not use a stack at all. This frees up rsp as a general purpose register, and, mostly for fun, I also made it use push and pop when writing/reading from a data structure if it was pointed to by rsp. I'm sure it would have posed an interesting challenge to reverse engineers.

Continuation Passing Style

Scott Encoding

In CPS Scott encoding correspods to a match operator.

Syntax and Sugar

Refrences

https://github.com/roc-lang/roc

https://legacy.cs.indiana.edu/~dyb/papers/3imp.pdf

https://arxiv.org/pdf/2009.05539

https://arxiv.org/pdf/2502.20546

Remco Bloemen
Math & Engineering
https://2π.com