Polyglot grammar library: convert between grammar languages.

Goal: to convert between ABNF, ANTLR4, Lark and Tatsu grammar languages without losses, provided enough configuration to translate between different semantics (e.g., ordered alternatives).

Current status: convert between internal grammar languages and ABNF.

• grammars.escapes: char-to-string serialization and parsing.
• model: base model and pure functions for grammar intermediate representation (IR).
• grammars.python_re_writer: write grammar model as Python's re regex syntax.
• optimizer: optimize rulemap-to-rulemap
• runtime: combine grammar and visitor class into an efficient runtime representation of rulemap+methodmap.
• recursive_parser: grammar parser implementation using top-down recursive descent.
• generate: generate text from grammar model.
• grammars.lisp: parse and serialize grammar IR in a Lisp language.
• grammars.ebnf: parse and serialize grammar IR in an EBNF-like language.
• grammars.abnf: parse and serialize grammar IR in a standard ABNF language.

digraph {
    grammars.escapes;
    model;

    grammars.python_re_writer -> grammars.escapes
    grammars.python_re_writer -> model

    optimizer -> grammars.python_re_writer
    optimizer -> model

    runtime -> model
    runtime -> optimizer

    recursive_parser -> model
    recursive_parser -> runtime

    generate -> model
    generate -> recursive_parser

    grammars.lisp -> model
    grammars.lisp -> grammars.escapes
    grammars.lisp -> recursive_parser

    grammars.ebnf -> grammars.escapes
    grammars.ebnf -> grammars.lisp
    grammars.ebnf -> model
    grammars.ebnf -> recursive_parser

    grammars.abnf -> grammars.lisp
    grammars.abnf -> model
    grammars.abnf -> recursive_parser
}