/// Keyword
token Token='token' Start='start' Right='right' Skip='skip' Part='part';
/// Punctuator
token Colon=':' Semi=';' Equal='=' LPar='(' RPar=')' LBrak='[' RBrak=']'
      Or='|' Star='*' Plus='+' Hat='^' Slash='/' Tilde='~' And='&';
/// Identifier for rules and tokens
token Id='<identifier>' Str='<string literal>';
token Predicate='<semantic predicate>' Action='<semantic action>' Assertion='<semantic assertion>';
token NodeRename='<node rename>' NodeMarker='<node marker>' NodeCreation='<node creation>';
token Comment DocComment Whitespace;

start file;
skip Comment DocComment Whitespace;

file: decl*;
decl^:
  token_list
| ?1 rule_decl
| start_decl
| right_decl
| skip_decl
| part_decl
;
start_decl: 'start' Id ';';
right_decl: 'right' (Id | Str)+ ';';
skip_decl: 'skip' (Id | Str)+ ';';
part_decl: 'part' Id+ ';';
token_list: 'token' token_decl+ ';';
token_decl: Id ['=' Str];
rule_decl: Id ['^'] ':' [regex] ';';

regex^: alternation;
alternation^: ordered_choice [('|' ordered_choice)+ >];
ordered_choice^: concat [('/' concat)+ >];
concat^: postfix [postfix+ >];
postfix:
  postfix '*' @star
| postfix '+' @plus
| '(' [regex] ')' @paren
| '[' regex ']' @optional
| Id @name
| Str @symbol
| Predicate @predicate
| Action @action
| Assertion @assertion
| NodeRename @node_rename
| NodeMarker @node_marker
| NodeCreation @node_creation
| '^' @node_elision
| '~' @commit
| '&' @return
;