Grammar railroad diagram

[mingodad]

Would be nice if this Grammar-Kit added an option to dump the grammar in an EBNF format understood by https://github.com/GuntherRademacher/rr to generate nice navigable railroad diagrams to hep document/develop/debug grammars.

I've also added https://github.com/JetBrains/Grammar-Kit/blob/master/grammars/Grammar.bnf to https://mingodad.github.io/parsertl-playground/playground/ an Yacc/Lex like online interpreter/editor (select Grammar-Kit parser from Examples then click Parse to see a parse tree for the content in Input source) and from there I generated an EBNF for railroad diagram (see bellow with instructions at the top).

//
// EBNF to be viewd at
//    (IPV6) https://www.bottlecaps.de/rr/ui
//    (IPV4) https://rr.red-dove.com/ui
//
// Copy and paste this at one of the urls shown above in the 'Edit Grammar' tab
// then click the 'View Diagram' tab.
//

grammar::=
	  grammar_element

grammar_element::=
	  attrs
	| rule
	| grammar_element attrs
	| grammar_element rule

rule::=
	  rule_start expression attrs_opt semi_opt

semi_opt::=
	  /*%empty*/
	| SEMICOLON

attrs_opt::=
	  /*%empty*/
	| attrs

rule_start::=
	  modifier_zom RULE_NAME OP_IS

modifier_zom::=
	  /*%empty*/
	| modifier_zom modifier

modifier::=
	  "private"
	| "external"
	| "meta"
	| "inner"
	| "left"
	| "upper"
	| "fake"

attrs::=
	  LEFT_BRACE attr_zom RIGHT_BRACE

attr_zom::=
	  /*%empty*/
	| attr_zom attr

attr::=
	  attr_start attr_value semi_opt

attr_start::=
	  id attr_pattern OP_EQ
	| id OP_EQ

attr_value::=
	  attr_value_inner

attr_value_inner::=
	  reference_or_token
	| literal_expression
	| value_list

attr_pattern::=
	  LEFT_PAREN string_literal_expression RIGHT_PAREN

value_list::=
	  LEFT_BRACKET list_entry_zom RIGHT_BRACKET

list_entry_zom::=
	  /*%empty*/
	| list_entry_zom list_entry

list_entry::=
	  id list_entry_tail_opt semi_opt
	| string_literal_expression semi_opt

list_entry_tail_opt::=
	  /*%empty*/
	| list_entry_tail

list_entry_tail::=
	  OP_EQ string_literal_expression

expression::=
	  sequence choice_opt

choice_opt::=
	  /*%empty*/
	| choice

sequence::=
	  option_zom

option_zom::=
	  /*%empty*/
	| option_zom option

option::=
	  predicate
	| paren_opt_expression
	| simple quantified_opt

quantified_opt::=
	  /*%empty*/
	| quantified

choice::=
	  OP_OR sequence
	| choice OP_OR sequence

quantified::=
	  quantifier

quantifier::=
	  OP_OPT
	| OP_ONEMORE
	| OP_ZEROMORE

predicate::=
	  predicate_sign simple

predicate_sign::=
	  OP_AND
	| OP_NOT

simple::=
	  reference_or_token
	| literal_expression
	| external_expression
	| paren_expression

external_expression::=
	  EXTERNAL_START reference_or_token option_zom EXTERNAL_END

reference_or_token::=
	  id

literal_expression::=
	  string_literal_expression
	| number

string_literal_expression::=
	  string

paren_expression::=
	  LEFT_PAREN expression RIGHT_PAREN

paren_opt_expression::=
	  LEFT_BRACKET expression RIGHT_BRACKET

//Tokens

OP_IS ::= "::="
OP_NOT ::= "!"
OP_AND ::= "&"
LEFT_PAREN ::= "("
RIGHT_PAREN ::= ")"
OP_ZEROMORE ::= "*"
OP_ONEMORE ::= "+"
SEMICOLON ::= ";"
EXTERNAL_START ::= "<<"
OP_EQ ::= "="
EXTERNAL_END ::= ">>"
OP_OPT ::= "?"
LEFT_BRACKET ::= "["
RIGHT_BRACKET ::= "]"
LEFT_BRACE ::= "{"
OP_OR ::= "|"
RIGHT_BRACE ::= "}"

number ::= [0-9]+
string ::= "'"("\".|[^'\#xA#xD])*"'"
string ::= '"'("\".|[^"\#xA#xD])*'"'

RULE_NAME ::= id
id ::= [A-Za-z_][A-Za-z0-9_-]*