grammar.owl

#using owl.v4

# This is the grammar for Owl itself.
# Compile with `owl -c grammar.owl -o src/1-parse.h`.

grammar = (rule | comment-token | custom-token | whitespace)*
rule = identifier '=' body
body = expr | (expr ':' identifier)+ operators*
operators = '.operators' fixity operator+
fixity =
  'postfix' : postfix-op
  'prefix' : prefix-op
  'infix' assoc : infix-op
assoc =
  'flat' : flat-op
  'left' : left-op
  'right' : right-op
  'nonassoc' : nonassoc-op
operator = expr ':' identifier
expr =
  identifier ('\\' ':' identifier@exception)* ('@' identifier@rename)? : ident
  string : literal
  [ '(' expr ')' ] : parens
  [ '[' string@begin-token expr\:choice? string@end-token ']' ] : bracketed
 .operators postfix
  '*' : zero-or-more
  '+' : one-or-more
  '?' : optional
  [ '{' (repetition | expr (',' repetition)?)? '}' ] : repetition
 .operators infix flat
  '' : concatenation
 .operators infix flat
  '|' : choice
repetition =
  integer@begin : exact
  integer@begin '+' : at-least
  integer@begin ',' integer@end : range
comment-token = '.line-comment-token' string | comment-token-v1
comment-token-v1 = 'line-comment-token' string
custom-token = '.token' identifier string*
whitespace = '.whitespace' string*

.line-comment-token '#'