Rejoice is a programming language released in April 2026 by Devine Lu Linvega of Hundred Rabbits — the artist-programmer pair who live and work on a sailboat. Its program state is not a stack, not an array, not a set of named variables. It is a bag: an unordered multiset of symbols where only kind and quantity matter, and position does not exist. Programs are sequences of fractions: owl/cat^2 means "if the bag contains two cats, replace them with one owl." A fraction's denominator specifies what to remove from the bag; its numerator specifies what to add. Each fraction is attempted in order — if it can fire, it fires; if not, it is skipped. When the program ends, what remains in the bag is the result. From this mechanism alone, without any additional primitives, emerge NOT gates, AND gates, arithmetic operations, Fibonacci sequences, and FizzBuzz.

In SAE terms, the already-construct here is stack-based concatenative computation — Forth and its descendants. The stack embeds a spatial metaphor at the heart of computation: elements occupy positions (top, bottom), push and pop are the basic operations, and meaning depends entirely on ordered slots. This is a solid construct — named, optimized, propagated as paradigm across decades of programming language design. Rejoice's chisel is the removal of position. A bag has no numbered seats; elements carry only count, not location. What remains when you strip position from computation is arithmetic over quantities — and that is exactly the natural language of fractions. The remainder, in this language, is literal: every fraction application subtracts its denominator from the bag, and what survives is a mathematical remainder. The program's output is, in the precise mathematical sense of the word, a remainder.

A second-order remainder: logic emerges from arithmetic. We ordinarily understand arithmetic as built on top of logic (logic gates → transistors → processor → arithmetic). Rejoice inverts this: NOT, OR, and AND gates are all implemented as sequences of fractions, with no independent Boolean primitive anywhere. Logic becomes the remainder of fraction arithmetic, not its foundation. This inversion is not a design goal — it is a natural product of the bag's structure, which can express "if this symbol is present in the bag" as a direct condition in fraction notation, allowing propositional logic to grow from arithmetic the way weeds grow through pavement. The documentation language enacts the same gesture: Peano's Latino Sine Flexione is what remains of Classical Latin after all grammatical inflection has been stripped away — the same structural chisel applied to natural language that Rejoice applies to computation. The text that records the language has been chiseled in the same way the language itself chisels computation.

Rejoice's remainder quality is still growing. On release in April 2026, Devine called it a "cursed idea" and asked practitioners of rewriting systems, linear logic, and multisets for help — because he himself stood at the edge of what he could understand. The mailing list was just established; the connection to Interaction Nets is still being explored (a Pocket Nets zine was released the same month); the relationship to tropical arithmetic has only just been named. The language's standard library is incomplete; its semantics are still changing; the creator doesn't yet know what it can fully express. This is precisely the condition of the remainder: sufficient clarity to be implemented, but not yet fully digested by any naming system. The moment it gets filed under "multiset rewriting language" or "constraint-based concatenative language," that naming act will crystallize it from remainder into construct. For now, it remains a bag of symbols without a proper name.

Rejoice runs on Uxntal — Hundred Rabbits' own minimal self-sufficient virtual machine, itself another instance of remainder aesthetics built into software infrastructure. A browser-embedded REPL is available at the link below. Write programs as fractions. Store computation as an unordered bag. No positions, no addresses, no sequence in the state — only what remains, among a pile of unordered things, when the fractions have finished firing.

Han Qin (秦汉) · @hqinjarsy · SAE Judgment & Aesthetics