uxntal syntax

uxntal is the primary programming language of the uxn virtual machine. While the interface of the underlying virtual machine has been frozen to further change, the language it hosts has been developed not towards a specification, but as a means to an end.

In practice, uxntal newcomers are active participants in the language's clarification and refinement, wanting (and often needing) guidance from the active ecosystem of users. While a majority of this clarification relates to the language semantics, the surface-level syntax is itself also a nuanced object which is difficult to communicate.

The purpose of this experiment is the notation of a generative grammar which shows a valid construction for every uxntal syntactic form. The rules showing these constructions are a much weaker version of the problem of notating a specification of the language: the set of generated programs being a conservative subset of all valid uxntal programs.

The generative grammar is given in a Bachus-Naur Form with two extensions.

First, as notation shorthands, take ␣ to be any amount of whitespace separation, <hex1> to be any hexadecimal character 0–f, and <hexn> a string of n hexadecimal characters (e.g., <hex2> encoding 00–ff, a byte).

Second, uxntal naming forms are defined as being not something, which resists BNF expression: instead, take as given: