Expressive grammars
EBNF groups, parameterized and inline rules, middle actions, multiple entries, imports, token aliases, explicit empty rules, and constructor parameters.
Extended grammar reference →EXPLICIT OPT-IN SURFACE
Raise the grammar’s ceiling.
Select pragma extended or --mode=extended for features that
enrich the grammar while lowering to the same deterministic parser pipeline.
Integrated lexing
Longest-match rules, lexical states, Unicode-aware locations, and streaming String, IO, or Fiber input are generated beside the parser.
Lexer migration guide →Trees and types
Error-tolerant CST output and @node Data ASTs can generate exhaustive
visitors, listeners, and semantic-value RBS.
Diagnostics and tooling
Exact expected tokens, conflict explanations, bounded ambiguity checks, formatting, LSP support, diagrams, grammar tests, and production coverage share versioned IR.
Inspect a grammar in the browser →