@tabnas/bnf

The shared compiler behind the BNF-family grammar front-ends for the tabnas parsing engine.

This package holds no notation of its own. It defines a grammar IR and compiles it into a tabnas GrammarSpec; a front-end parses one concrete syntax into that IR:

ABNF / GBNF / EBNF text ──front-end──▶ Grammar ──emitGrammarSpec──▶ GrammarSpec

| Front-end | Notation | |---|---| | @tabnas/abnf | RFC 5234 ABNF | | @tabnas/gbnf | llama.cpp GBNF | | @tabnas/ebnf | EBNF (best effort) |

const { emitGrammarSpec } = require('@tabnas/bnf')

const spec = emitGrammarSpec({
  productions: [
    { name: 'val', alts: [[{ kind: 'ref', name: 'add' }]] },
    { name: 'add', alts: [[{ kind: 'token', name: '#NR' }]] },
  ],
}, { tag: 'demo' })

Everything downstream of the IR is shared and lives here: desugaring repetition into helper rules, left-recursion elimination, tail-repeat rewriting, the probe/rewind dispatcher for prefixes beyond the engine's bounded lookahead, literal lifting, token allocation, first-set analysis, and $stepN chain emission.

Full documentation, including the IR contract and the options table, is in the repository README.

Install

npm install @tabnas/bnf @tabnas/parser

License

MIT. Copyright (c) 2026 tabnas.